Naked Science Forum

On the Lighter Side => That CAN'T be true! => Topic started by: Aemilius on 21/11/2013 18:49:57

Title: What is Free Fall?
Post by: Aemilius on 21/11/2013 18:49:57
So.... What does Free Fall really mean?

Title: Re: What Is Free Fall?
Post by: alancalverd on 21/11/2013 23:00:06
The condition under which a body is, literally, free to fall under the influence of the local gravitational field with no resistance to its acceleration.
Title: Re: What Is Free Fall?
Post by: CliffordK on 21/11/2013 23:28:14
Is air/wind resistance a component of free fall?  It is negligible at low speeds, but can be significant as one reaches terminal velocity.

So, I would think a sky diver would be considered in "free fall" from the instant he jumps out of the plane, until he deploys the chute, even though one has air resistance on the body, as well as the chute.

Perhaps it all depends on how strict of a definition one uses.
Title: Re: What Is Free Fall?
Post by: Aemilius on 21/11/2013 23:33:12
The condition under which a body is, literally, free to fall under the influence of the local gravitational field with no resistance to its acceleration.

So, there can't be anything in the way.... Not even a little resistance?
Title: Re: What Is Free Fall?
Post by: alancalverd on 21/11/2013 23:37:36
No, a sky diver is not in free fall, but in a fairly good approximation to it during the acceleration phase. The duration of this phase depends on the configuration he adopts, which will determine his terminal speed and hence the time taken to reach it.

The colloquial use of the term covers falling through air resistance but it isn't strictly correct.
Title: Re: What Is Free Fall?
Post by: Aemilius on 21/11/2013 23:59:26

The colloquial use of the term covers falling through air resistance but it isn't strictly correct.

So, generally, in an everyday terrestrial sense, the colloquial use of the term "free fall" describes objects falling through air, even if not strictly correct. For example, a 100 pound weight falling from, say, a height of fifteen feet....  Could it reasonably be said to be in "free fall", or gravitational acceleration, so long as there's nothing in the way?

(https://web.archive.org/web/20151125114607im_/http://picasion.com/pic76/9383be58c2196650abf48981db503779.gif)
Title: Re: What Is Free Fall?
Post by: CliffordK on 22/11/2013 07:23:49
A compact 100 lb piece of steel falling over a short distance, starting at zero velocity, in Earth's atmosphere would generally meet alancalverd's definition of free fall.

Dropping it in the ocean, and it would encounter sufficient resistance to not be in free fall.

Likewise, if your 100 lb weight was a hang glider, it wouldn't drop with free fall.
Title: Re: What Is Free Fall?
Post by: alancalverd on 22/11/2013 09:35:36
No! Ask any bombardier or artilleryman! Even a nicely tapered penetration shell needs some correction for air resistance in the fall.

I weigh well over 100 lb and frequently pilot aircraft (some without engines) weighing a lot more. Fortunately there's a heck of a difference between a controlled glide and free fall. As I stated earlier, terminal speed depends on the configuration of the falling object in a viscous medium - a sailplane with the flaps deployed falls a lot slower than a helicopter with the rotor coned. And of course if you point a powered aeroplane at the ground and open the taps, it will accelerate a lot faster than g, but still only to a terminal speed.

In the absence of air, and with a sufficiently dense gravitational source, you have a black hole, whose terminal speed for all falling objects is c. I have yet to encounter one in civilian airspace, but I'm told there may be something of interest around Bermuda.
Title: Re: What Is Free Fall?
Post by: Aemilius on 22/11/2013 10:36:21
Right.... but I'm just talking about a 100 pound weight falling from around 15 feet.

So there can't be any resistance, not even a little.... Right? I mean, if there's any resistance at all (other than air), then obviously you won't get free fall, since some of the gravitational potential energy would be used to overcome the resistance and it wouldn't all be converted to motion. The fall times for the two 100 pound weights below, falling about 15 feet, should never be the same.... True?

(https://web.archive.org/web/20151125114607im_/http://picasion.com/pic75/25bd5d8b9f31bb7a59bb3a25fd6f15bd.gif)
Title: Re: What Is Free Fall?
Post by: alancalverd on 22/11/2013 14:09:17
Absolutely. If the weights are identical and sufficiently dense, and the frangible impedance sufficiently large, you should be able to measure the difference in arrival times.
Title: Re: What Is Free Fall?
Post by: Don_1 on 22/11/2013 20:34:12
What Is Free Fall?


Put quite simpley, it's wheAAGHHHHHHHHHHhhhhhhhh      \*SPLAT*/
Title: Re: What Is Free Fall?
Post by: Aemilius on 22/11/2013 22:22:32
So, here's our 100 pound weight again, now sitting atop a 15 foot tall column. It really doesn't matter what the column's made of, all that matters is that as long as it remains undamaged, it's fully capable of indefinitely supporting the 100 pound weight.
 
Now I want the column to fail, without the addition of any external force, in such a way that the 100 pound weight goes into free fall. That can't that happen can it? I mean, the column would have to at least be damaged for failure to occur. Even then.... It couldn't come down at free fall compared to the same weight dropped from the same height at the same time falling through air could it?
 
(https://web.archive.org/web/20151125114607im_/http://picasion.com/pic75/6baf7e1620b925d764f60ccc6dc222f0.gif)
Title: Re: What Is Free Fall?
Post by: alancalverd on 23/11/2013 03:54:38
Just pull the column out of the way, sideways. Or push the weight off the column (probably easier to do!)
Title: Re: What Is Free Fall?
Post by: Aemilius on 24/11/2013 05:45:40
Just pull the column out of the way, sideways. Or push the weight off the column (probably easier to do!)


So, one could pull, or knock out the column, causing the 100 pound weight on top of the column to go into free fall just like the 100 pound weight being dropped on the right....
 
(https://web.archive.org/web/20151023215653im_/http://picasion.com/pic75/1663de40a7bf83c865aa619bbf382767.gif)

Or, one could simply push the 100 pound weight off the top of the column, causing the 100 pound weight on the column to go into free fall just like the 100 pound weight being dropped on the right....

(https://web.archive.org/web/20151023215653im_/http://picasion.com/pic75/6f92b6a1f1edaf2ee8415537286df845.gif)

One might even use a small explosive charge to fragment the column (bottom), causing the 100 pound weight on the column to go into free fall just like the 100 pound weight being dropped on the right....

(https://web.archive.org/web/20151023215653im_/http://picasion.com/pic75/58726ac604f62becf4def0e09c064b22.gif)
Title: Re: What Is Free Fall?
Post by: alancalverd on 24/11/2013 09:48:39
I'm in strict pedant mode today.

1. It still isn't free fall. The acceleration of the object will depend on its shape.

2. An explosive charge will have some upward force component and the debris and expanding gas beneath the object will have a different composition from the air under the other mass, so its behaviour will be different depending on the nature of the trigger event..

3. Where did the second mass come from? Something must have been holding it up before the explosion!
Title: Re: What Is Free Fall?
Post by: Aemilius on 24/11/2013 20:06:46
I'm in strict pedant mode today.

I appreciate your pedantry.... You're a way out cat man (complimentary)!

1. It still isn't free fall. The acceleration of the object will depend on its shape.

I see your point.... Would it be reasonable to say though in just a general every day terrestrial sense, that the effect any aerodynamic properties might have on the 100 pound weights fall time (being a relatively compact object) falling from a height of 15 feet could be considered negligible, or do we need to switch to an in vacuo environment to eliminate it as a concern? I don't have any preference.
 
2. An explosive charge will have some upward force component and the debris and expanding gas beneath the object will have a different composition from the air under the other mass, so its behaviour will be different depending on the nature of the trigger event.

Understood.... Do you think though for the time being, we could just assume a carefully engineered charge whose total upward force (the explosion, the expanding debris and the expanding gas components combined) is equal to 100 pounds so that it wouldn't lift the weight in the process of destroying the column? Just to render it negligible for the sake of general discussion.   

3. Where did the second mass come from? Something must have been holding it up before the explosion!

I think the weight that appears on the right (they're just general schematic animations) just as each scenario begins to unfold would be what you science guys call a "control" meant to be held up as a standard, or visual aid, to compare various possible scenarios (on the left) and generally illustrate what could reasonably be expected to occur compared to an identical control (on the right) under identical conditions at the same time....   

(https://web.archive.org/web/20151125114607im_/http://picasion.com/pic75/25bd5d8b9f31bb7a59bb3a25fd6f15bd.gif)

The falling weight on the right is the same in all the animations. Does that make sense? I sort of described it earlier....

"For example, a 100 pound weight falling from, say, a height of fifteen feet...."

(https://web.archive.org/web/20151125114607im_/http://picasion.com/pic76/643d1abfbb6bad05dcae64eaf0194752.gif)
Title: Re: What Is Free Fall?
Post by: alancalverd on 25/11/2013 08:24:09
Just thinking about aircraft I've flown in the past reminded me of a hot air balloon that weighed about 4 tons but happily flew upward under some semblance of control. The three principles of flight are configuration, configuration, configuration!

Anyway your "control", in order to be scientifically valid, must differ from the test object only in known ways, so we can't have a control that appears by magic at height h and velocity zero at the same time as the magical explosion that imparts no force and leaves no debris - too many unknowns!

So what you are asking is "if I  push two identical rocks off a cliff at the same time, will they reach the ground together?" 

To which the pedantic answer is "that is the definition of 'identical'". Even a crap physicist like Aristotle would have agreed.
Title: Re: What Is Free Fall?
Post by: Aemilius on 25/11/2013 10:38:56
Right, I see your point. These animations are inadequate. I'll take another tack.

From my last post.... Would it be reasonable to say though in just a general every day terrestrial sense, that the effect any aerodynamic properties might have on the 100 pound weights fall time (being a relatively compact object) falling from a height of 15 feet could be considered negligible, or do we need to switch to a vacuum to eliminate it as a concern? 

By the way.... thanks for responding.
Title: Re: What Is Free Fall?
Post by: alancalverd on 25/11/2013 11:36:11
You will recall (had you been awake in Physics 101!) that s= ut + 0.5at2

where s = distance, t = time and a = acceleration

in vacuo, say s = 15 and a = 32. u=0, so 0.5 x 32 x t2 = 15, t= sqrt(15/16) = 0.9682 seconds

v = u + at, so speed on hitting the ground = 32 x .9682 = 30.98 ft/sec. This is a long way below the terminal speed of a cannon ball so you would find it difficult to measure the difference between in vacuo and in air arrival times. 

However http://arc.id.au/CannonballDrag.html (http://arc.id.au/CannonballDrag.html) shows some surprising results, including a sharp decrease in drag at relatively high Mach numbers - but it's all very dependent on the shape of the projectile, so you can't easily extrapolate from a cannon ball to any other lump of iron.

In respect of
Quote
any aerodynamic properties
I repeat that a 100 lb glider will take a lot longer to hit the ground than a 100 lb cannon ball. 
Title: Re: What Is Free Fall?
Post by: Aemilius on 25/11/2013 22:32:40
And you would recall (had you been awake in English 101!) that it's best to read the entire question before answering. It doesn't say anything about 100 pound cannon balls at relatively high Mach numbers or 100 pound hang gliders wafting around in the upper atmosphere....

Would it be reasonable to say though in just a general every day terrestrial sense, that the effect any aerodynamic properties might have on the 100 pound weights fall time (being a relatively compact object) falling from a height of 15 feet could be considered negligible, or do we need to switch to an environment in vacuo to eliminate it as a concern?

Does that help? It's basically a "yes" or "no" interogative. Instead of all this....

You will recall (had you been awake in Physics 101!) that s= ut + 0.5at2

where s = distance, t = time and a = acceleration

in vacuo, say s = 15 and a = 32. u=0, so 0.5 x 32 x t2 = 15, t= sqrt(15/16) = 0.9682 seconds

v = u + at, so speed on hitting the ground = 32 x .9682 = 30.98 ft/sec. This is a long way below the terminal speed of a cannon ball so you would find it difficult to measure the difference between in vacuo and in air arrival times.
However http://arc.id.au/CannonballDrag.html shows some surprising results, including a sharp decrease in drag at relatively high Mach numbers - but it's all very dependent on the shape of the projectile, so you can't easily extrapolate from a cannon ball to any other lump of iron.

In respect of

Quote
any aerodynamic properties

I repeat that a 100 lb glider will take a lot longer to hit the ground than a 100 lb cannon ball.

....a simple "Yes, it would be reasonable to say that the effect any aerodynamic properties might have on a 100 pound weights fall time (if it's a relatively compact object) falling from a height of 15 feet could be considered negligible." would've been fine.
Title: Re: What Is Free Fall?
Post by: alancalverd on 25/11/2013 23:32:37
"Relatively compact": relative to what?

"Negligible": compared with what?

You may recall that a signal apparently delayed by less than a nanosecond over a distance of 750 kilometers caused a major rumpus about a year ago because it implied that neutrinos travelled faster than light, which would have upset our entire understanding of the universe. 

Sorry, chum, physics demands the precise use of language. There's nothing "reasonable" about the physical universe - it either is or it isn't. Except of course for Schrodinger's Cat, which is a very precise "maybe".

Even when the lump of iron isn't moving, we make corrections for the relative buoyancy of weights in air when comparing masses!
Title: Re: What Is Free Fall?
Post by: Aemilius on 26/11/2013 06:22:27
Let me take another tack. The previous animations were inadequate for all the reasons you mentioned, so now it all takes place in a vacuum.... no more aerodynamic properties involved. A release mechanism has been added so that the 100 pound weight is no longer just hanging there in space.

(https://web.archive.org/web/20151125114607im_/http://picasion.com/pic76/78fe757793d30a322732edd16cff4bde.gif)

Before I make any more animations.... Is this an acceptable schematic format? 
Title: Re: What Is Free Fall?
Post by: alancalverd on 26/11/2013 07:11:50
I think we have agreed on the definition of free fall. No need for animations, but I'm impressed with yours.
Title: Re: What Is Free Fall?
Post by: Aemilius on 27/11/2013 03:11:53
I think we have agreed on the definition of free fall.

I think I'm actually learning something.... Olympic! 

No need for animations, but I'm impressed with yours.

Thanks! While I'm coming up with what to do next, would you mind if I ask what your background is alancalverd? You seem to have the math down pretty good.... College man?
Title: Re: What Is Free Fall?
Post by: Aemilius on 28/11/2013 07:49:42
With the last animation, I showed (schematically) rate of descent, distance travelled and time elapsed for the 100 pound weight being used as a control that appears on the right in all the animations.

It seems reasonable that since the control that appears (on the right) just as each scenario begins to unfold consistently descends at the same rate, travels the same distance, in the same elapsed time in all the animations, that I should be able to keep using it as a standard, or visual aid, for comparison with various possible scenarios (on the left). It's easier than including the clamp release mechanism, measurements and labels in every single animation....

(https://web.archive.org/web/20151125114607im_/http://picasion.com/pic76/ef2992a1bed34a1ad9d2e8f520c5ad7e.gif)

I'm thinking, with just a little imagination, when the control appears on the right in each animation, that it can be seen as entering the picture at the moment it's released from the clamp mechanism, and also signal the beginning of the comparison....

(https://web.archive.org/web/20151125114607im_/http://picasion.com/pic76/094913e578a7dcbe17460c6678bbde98.gif)

Is that acceptable?
Title: Re: What Is Free Fall?
Post by: alancalverd on 28/11/2013 08:55:33
The problem is that the "control" does not move in sync with the "clamp" unit, so it's very confusing. And I still don't like the idea of the "control" appearing ex nihilo - even worse when it appears and moves at random times! Once you have established the free fall time from the clamp, you can just refer to the number without having to replicate the test in each animation.

For what it's worth, I have a PhD in experimental physics, about 45 years' experience in various branches of engineering for medical radiation, and enough studies in aviation to fly myself to work. But this stuff is all covered at school level!
Title: Re: What Is Free Fall?
Post by: Aemilius on 28/11/2013 09:51:26
The problem is that the "control" does not move in sync with the "clamp" unit, so it's very confusing. And I still don't like the idea of the "control" appearing ex nihilo - even worse when it appears and moves at random times! Once you have established the free fall time from the clamp, you can just refer to the number without having to replicate the test in each animation.

Right, understood.... I removed the un-labeled control animation from right next to the Control Details animation.... I'll correct it for the sake of sychronicity. As far as the ex nihilo appearance of the control goes, I put a link to the details beneath each animation.   

For what it's worth, I have a PhD in experimental physics, about 45 years' experience in various branches of engineering for medical radiation, and enough studies in aviation to fly myself to work. But this stuff is all covered at school level!

For what it's worth? Man.... I'd say that's worth a great deal! I know all that's covered in school, but I'm trying to resolve something I read about. If you give me just a little more time, and can suffer through a few more animations to confirm what should happen in just a few more scenarios, I'll get to it.
 
Again, nice to meet you and very much appreciate your responses.
Title: Re: What Is Free Fall?
Post by: Aemilius on 28/11/2013 10:31:00
While we're off topic for a post or two exchanging background information, I'm an Artist. Here's one of my drawings, I hope you enjoy it....

"The Temple".... A Pen and Ink drawing done with a Rapidograph drafting pen that draws a line about the width of a human hair. About 20x24 inches. All freehand (no measurements or preliminary sketch), loosely modeled on a ruined Roman style temple in Turkey I saw a picture of once. The technique is stippling (dots). It took about four hundred hours.

(https://web.archive.org/web/20151125115847im_/http://s28.postimg.org/5wqcfef65/Untitled1.jpg)
Title: Re: What Is Free Fall?
Post by: Aemilius on 28/11/2013 10:55:21
I synchronized the animations (reply 24).
Title: Re: What Is Free Fall?
Post by: alancalverd on 28/11/2013 11:11:34
Impressive drawing! My artistic skills stop at machine blueprints and printed circuits.

The sync is a little better but still jerky and "A then B",which doesn't make the point. Not sure what program you are using to generate the animation but if I wanted to show this in Powerpoint I'd group the two objects together so they fall as one. After all, that's what Galileo demonstrated.
Title: Re: What Is Free Fall?
Post by: Aemilius on 28/11/2013 12:35:24
Impressive drawing! My artistic skills stop at machine blueprints and printed circuits.

Thanks.... glad you liked it. 

The sync is a little better but still jerky and "A then B",which doesn't make the point. Not sure what program you are using to generate the animation but if I wanted to show this in Powerpoint I'd group the two objects together so they fall as one. After all, that's what Galileo demonstrated.

Hah! I'm flattered you thought I was using a program but.... I am the program. I produced all the individual images that went into each animation one by one and then animated them using a site called "Picasion" (maximum of ten images per animation). They were done the same way I do everything else, with no measurements. I'm sure I could make them much smoother using a site that permits more images per animation, but then, it would take me considerably longer to produce them.

You didn't seem to have any trouble with the "frangible impedance" animation (reply #8), and they're fairly straightforward. It shouldn't be a long thread.... Can you work with them as they are?
Title: Re: What Is Free Fall?
Post by: alancalverd on 28/11/2013 20:35:48
If I was presenting this in  a lecture, I'd start with just the clamp release, then show a slide of the clamp and the "control" with the explanation that from now on we will be keeping the idealised object on the right as a constant reminder of what happens to an object in free fall. Then you can develop all sorts of scenarios on the left. Once you have said the magic word "idealised" you can get away with murder in physics. My dad swore he saw an Indian exam paper that said "you may ignore the weight of the elephant..."
Title: Re: What Is Free Fall?
Post by: Aemilius on 28/11/2013 21:25:53
If I was presenting this in  a lecture, I'd start with just the clamp release, then show a slide of the clamp and the "control" with the explanation that from now on we will be keeping the idealised object on the right as a constant reminder of what happens to an object in free fall. Then you can develop all sorts of scenarios on the left.

How about this....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/ef2992a1bed34a1ad9d2e8f520c5ad7e.gif)

"The idealised object, or Control, depicted on the right in all the animations is for comparison as a constant reminder of what happens to an object in free fall. Scenarios in all the animations will be depicted on the left."

Is that acceptable?


My dad swore he saw an Indian exam paper that said "you may ignore the weight of the elephant..."

Hilarious!
Title: Re: What Is Free Fall?
Post by: alancalverd on 29/11/2013 00:13:29
And just one more niggle - though this may be the point you are trying to make - the mass of the objects is irrelevant. In free fall, all objects fall at the same rate.
Title: Re: What Is Free Fall?
Post by: Aemilius on 29/11/2013 01:06:06
And just one more niggle - though this may be the point you are trying to make - the mass of the objects is irrelevant. In free fall, all objects fall at the same rate.

I'm aware of that. I merely thought that since the thread started out with the consideration of a falling 100 pound weight that I would continue with that assigned value for the sake of consistency. Also, if we return later to consideration of the same weight falling through air, the weight of it will not have to be reiterated or added to already existing animations, as they would have had I proceeded without them.

I "Googled" your name Mr. Calverd. Again, very much appreciate your taking the time to respond, now even more than before.... I'm sure you're a very busy man indeed! 
Title: Re: What Is Free Fall?
Post by: Aemilius on 29/11/2013 04:03:16
Additionally.... There are also a couple of animations that will have to do with weakening/overloading and subsequent failure of a column where the weight of the object sitting atop it would obviously be a factor, whether in air or in vacuo. I'm working on those now (as time permits).
Title: Re: What Is Free Fall?
Post by: Aemilius on 29/11/2013 23:03:13
So I want to return to the 100 pound weight sitting atop a 15 foot tall column. For these two examples the material the column is made of may vary as long as the column, when undamaged, is fully capable of indefinitely supporting the 100 pound weight.

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic75/6baf7e1620b925d764f60ccc6dc222f0.gif)

If the column is weakened and fails, it would be a progressive failure. In other words.... There's no way it could naturally fail in such a way that the 100 pound weight would go into free fall in the same way as the control on the right.

In the first example, the column supporting the weight is made of a material susceptible to weakening by the application of heat. In the animation, weakening due to heating causes the column to lose strength and buckle as it fails. It seems reasonable to assume that if bifurcation of the column occurred at some point as the failure of the column progressed it might result in a small percentage of the total fall time being made up of free fall, but obviously, it couldn't go into free fall like the control on the right....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/171da9bd639a474f93f75416474f53ce.gif)

In the second example, the column supporting the weight is made of a material susceptible to weakening by being fractured. In the animation, weakening due to fracturing causes it to crumble, or fragment, as it fails. I know that more than likely it would slow and then topple over rather than continue straight down.... It's just a schematic representation. In this example, there would be no possibility of any bifurcation occuring at any point that could lead to even a small percentage of the total fall time being made up of free fall....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/189367ead1f1173ae0821bc21a4cb949.gif)
Title: Re: What Is Free Fall?
Post by: Aemilius on 30/11/2013 19:12:04
Here's the 100 pound weight again, now held by the clamp above a 15 foot tall column. For these two examples the material the column is made of may vary as long as the column, when undamaged, is not capable of supporting the 100 pound weight. The clamp initially holds the weight above the column. The top of the column is only in contact with the weight, not supporting it, while the weight remains in the clamp.

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/7200674bef6c01394366cef79909a65b.gif)

If the column fails under the 100 pound weight, again, it would be a progressive failure, similar in some ways to the last two examples. In other words.... There's no way it could naturally fail in such a way that the 100 pound weight would go into free fall in the same way as the control on the right.

In the first example, the column beneath the weight that's initially held by the clamp is made of a material susceptible to buckling when overloaded. In the animation, overloading causes the column to buckle as it fails. Again, it seems reasonable to assume that if bifurcation of the column occurred at some point as the failure of the column progressed it might result in a small percentage of the total fall time being made up of free fall, but it obviously couldn't go into free fall like the control on the right....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/a338ba3cef6cdac0cc13fe19a7c5c2bc.gif)

In the second example, the column beneath the weight that's initially held by the clamp is made of a material susceptible to fracturing when overloaded. In the animation, overloading causes it to fracture, crumble and fragment as it fails. Again, I know that more than likely it would slow and then topple over rather than continue straight down.... It's just a schematic representation. In this example, there would be no possibility of any bifurcation occuring at any point that could lead to even a small percentage of the total fall time being made up of free fall....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/491b34f1ef51fec27a6311f7b36e362d.gif)
Title: Re: What Is Free Fall?
Post by: alancalverd on 01/12/2013 07:55:15
I'm waiting with bated breath for the moment when Bin Laden's face appears in the smoke, or the lizard changes into George W Bush.
Title: Re: What Is Free Fall?
Post by: RD on 01/12/2013 08:26:54
... I'm sure I could make them much smoother using a site that permits more images per animation, but then, it would take me considerably longer to produce them. 

Cheating is possible : free software like GIMP (http://en.wikipedia.org/wiki/GIMP) will do inbetweening (http://en.wikipedia.org/wiki/Inbetweening) ...

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F189367ead1f1173ae0821bc21a4cb949.gif&hash=23a76c51de204084df65fcf9bc6431a7) [ Invalid Attachment ]
Title: Re: What Is Free Fall?
Post by: Aemilius on 01/12/2013 09:05:07
Hi RD (nice to meet you).... very cool, I'll check it out.
Title: Re: What Is Free Fall?
Post by: Aemilius on 01/12/2013 09:28:18
I'm waiting with bated breath for the moment when Bin Laden's face appears in the smoke, or the lizard changes into George W Bush.

Did you have something on your mind Mr. Calverd?
Title: Re: What Is Free Fall?
Post by: Aemilius on 01/12/2013 19:22:56
So I want to look at the clamp release thing again. In this example, the conditions under which the scenario weight falls will be obscured by a 15 foot tall blind. The conditions below the weight as it falls aren't visible....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/78fe757793d30a322732edd16cff4bde.gif)

Another way to know what conditions the weight fell under, besides actually being able to see the scenario weight or into the space beneath it, is by just looking at how the attached red marker moves compared to the control. Putting the marker on the scenario weight makes the distance from the bottom of the scenario weight, at 15 feet, to just under the red marker, another 15 feet, a total of 30 feet (plus the red marker).

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/f14e129d21b59409886a10b0c95e433b.gif)

The scenario with the control included is....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/255b5e6b0f1f20b0bd95d84a94ef1386.gif)

Then put the 15 foot blind in front of the space beneath the scenario weight. If the scenario weight falls 15 feet, the marker will be visible just above the 15 foot tall blind at the same height the scenario weight was at before it was released.

As usual, the comparison begins with the opening of the clamp and the appearence of the control. In the animation, comparing the marker to the control shows that the scenario weight came down at free fall, there absolutely can't have been anything beneath the scenario weight that would've tended to impede it's progress ....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/1036ed956866bb76e5e518d9c4e7a69c.gif)

By the same token, if there's anything at all beneath the scenario weight that would tend to impede its progress the marker will (to one degree or another) descend at a slower rate than the control. In the animation, comparing the marker to the control shows that the scenario weight came down at less than free fall, there must've been something beneath the scenario weight that tended to impede it's progress....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/dd7a80677f1571010a3f9b8cb03db7ef.gif)
Title: Re: What Is Free Fall?
Post by: alancalverd on 01/12/2013 23:28:30
So far, so obvious. I'm sure this is leading somewhere. Can we cut to the chase?
Title: Re: What Is Free Fall?
Post by: Aemilius on 02/12/2013 09:31:45
So far, so obvious. I'm sure this is leading somewhere. Can we cut to the chase?

Sure. Like I said earlier, it has to do with something I read about, a building collapse. The name of the building or where it was located.... I'm not really interested in that. I just want to know how it could have gone into free fall as a result of a progressive structural failure. The NIST has apparently confirmed that it went into free fall, after doing a formal pixel by pixel analysis of the video, for 2.25 seconds (8 stories, or approximately 105 feet).
[img[https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/6c7cd2005f1c75d081a720e434c5c713.gif[/img]http://

Just like my scenario though, in the video, we can't see into the space beneath the visible falling portion of the building because of other buildings (blue) in the foreground....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic76/0d8f489c42d14f50777e0d8e90059b6a.gif)

So that's what I'm curious about. The way the building came down is consistent with free fall acceleration....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic75/8db27a83092f9cb1be47bba39ea92628.gif)

But if free fall occured, and it was a progressive failure, it would seem to end us up in a rather awkward, even impossible situation like this....

(https://web.archive.org/web/20151125115847im_/http://picasion.com/pic75/9fda7447ab53a056ff5f02c28634ecb3.gif)

We can't have it both ways can we? What's your take?
Title: Re: What Is Free Fall?
Post by: Aemilius on 02/12/2013 11:17:42
Am I missing something?
Title: Re: What is free fall?
Post by: alancalverd on 02/12/2013 16:30:18
Difficult to comment without seeing the actual video, but a lot depends on the internal structure of the building.

Consider a simple brick-built shed with a pitched, trussed roof (I've just rebuilt one!)

If you had a gas explosion near the base of the building, the bricks would blow outwards but the roof would remain fairly intact as the trusses can withstand tension as well as compression, so the entire roof would fall like a parachute. Now blow away the roof tiles (which will happen after a few seconds' descent, because shingles are only intended to support forces from outside)  and the "parachute" approximates to your dense weight.

I can envisage a building where progressive failure in the lowest part of the walls becomes explosive as the upper part and roof accelerates downwards, with the lower walls bursting like an aneurysm under the increased internal pressure. In its simplest form the model is a cylinder whose walls are supporting a weighted piston. Once the cylinder begins to give way, the piston starts to compress the air inside and bursts the walls, which then allows the piston to fall. The total outward aerostatic force on the walls, once the building starts to collapse, equals the weight of every part that is no longer supported. Very few buildings (apart from nuclear power stations and the like) are designed to withstand outward force.   
Title: Re: What is free fall?
Post by: Aemilius on 03/12/2013 00:57:33
Difficult to comment without seeing the actual video, but a lot depends on the internal structure of the building.

Right. Here's a schematic rendering of the building, the video of the collapse the NIST used, and also the arrangement of the 81 steel support columns that held it up showing where the progressive failure began. Column 79 fails first (due to heating), followed in rapid succession by the other 80* columns.

*Correction.... 12 columns were damaged prior to column 79 failing, leaving 68 columns.

(https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcSklbwpclTzlpa-el8g5q5ZZ2tWXiHrtSb6iImUFVqnVMpdccVt)    (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fstream1.gifsoup.com%2Fview3%2F2051328%2Fwtc-7-collapse-o.gif&hash=5723d76ecbff20ccdbc7c5e8d1d9f5d0)   
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Faac5a25efe2b0286506472d4f1cea48e.gif&hash=e28ecec4a23d6821f77658a9a411d5d6)

Consider a simple brick-built shed with a pitched, trussed roof (I've just rebuilt one!)

Sounds like quite a project. You should post a picture.... I'd like to see that!

If you had a gas explosion near the base of the building, the bricks would blow outwards but the roof would remain fairly intact as the trusses can withstand tension as well as compression, so the entire roof would fall like a parachute. Now blow away the roof tiles (which will happen after a few seconds' descent, because shingles are only intended to support forces from outside) and the "parachute" approximates to your dense weight.

Makes sense, but no natural gas or other explosives were in the building. There was stored diesel fuel though, which is said to have contributed to a couple of the 5 or 6 fires that burned here and there on various floors throughout the building.

I can envisage a building where progressive failure in the lowest part of the walls becomes explosive as the upper part and roof accelerates downwards, with the lower walls bursting like an aneurysm under the increased internal pressure. In its simplest form the model is a cylinder whose walls are supporting a weighted piston. Once the cylinder begins to give way, the piston starts to compress the air inside and bursts the walls, which then allows the piston to fall. The total outward aerostatic force on the walls, once the building starts to collapse, equals the weight of every part that is no longer supported. Very few buildings (apart from nuclear power stations and the like) are designed to withstand outward force.

That makes sense too, but in this case, at the point the building went into free fall, it hadn't descended far enough to have developed the kind of extreme internal presurization that would have been needed to blow out the walls, windows and steel columns over a span of 8 stories. Even if it had, the built up pressure would have blown out windows to relieve/vent the accumulated pressure, not steel columns.
Title: Re: What is free fall?
Post by: alancalverd on 03/12/2013 15:52:49
Very little pressure is required to blow out a building. If my "idealised shed" roof fell one third of the height of the building, the excess internal pressure would be over 700 lb per square foot. Windows - especially large ones - give way well below that level, and the rigidity of a modern bulding is partly conferred by the stressed skin window structure. 

A lot of work was done on this sort of phenomenon in the early days of nuclear warfare, where most of the damage is caused by the compression and rarefaction waves, but most of the buildings I have seen tested were either wooden huts (inherently more burstproof structure) or concrete bunkers designed for the purpose of withstanding rarefaction.   

Once a couple of steel uprights have buckled, the stress on the remainder is no longer compressive but rotational, and they aren't good at sustaining a rotational load.

My recent construction was actually renovating an old barn: we've replaced several wooden uprights with brick or steel columns and strengthened the roof timbers. This was only possible at an economic cost because the original roof was made from overdesigned tied trusses so the framework could be cut and patched piece by piece without the whole lot collapsing. Modern roof structures tend to be minimally rigid and more difficult to repair. It looks very much as though the video'd building was also minimally rigid.
Title: Re: What is free fall?
Post by: Aemilius on 03/12/2013 20:34:10
Thanks Mr. Calverd. Busy day ahead.... will get back to this.
Title: Re: What is free fall?
Post by: Aemilius on 04/12/2013 01:09:39
Unrelated, but, I was just thinking (after a couple of shots of whiskey)....  How remarkable is it for an eighth grade high school dropout to ever have the chance to enjoy any kind of meaningful exchange with a career Ph.D. research Physicist?
 
Even as a 55 year old (relative) newcomer to the internet.... Far out man!

Thanks in advance Mr. Calverd.
Title: Re: What is free fall?
Post by: alancalverd on 04/12/2013 06:50:15
Not nearly as remarkable as being asked a sensible question by someone who seems to care about the answer!

Keep drinking the good stuff.
Title: Re: What is free fall?
Post by: evan_au on 04/12/2013 10:09:52
Reply #44 shows a graph of the building's velocity vs time.

The part outlined in red shows an approximately linear velocity vs time curve. This is representative of a building in free fall.

During this time period, the height of the building vs time would be parabolic, with the height proportional to the time squared.
Title: Re: What is free fall?
Post by: Aemilius on 04/12/2013 15:05:39
Hello evan_au (nice to meet you)....

Sorry, I should've mentioned earlier that the graph is from the NIST report (I'm sure I can dig up a link if necessary).

Are you also a Physicist?
Title: Re: What is free fall?
Post by: Aemilius on 04/12/2013 15:37:09
Just noticed your "Profile". Telecommunications.... Electrical Engineer?
Title: Re: What is free fall?
Post by: Pmb on 04/12/2013 17:43:42
Is air/wind resistance a component of free fall?  It is negligible at low speeds, but can be significant as one reaches terminal velocity.
It's wrong to say that It is negligible at low speeds because what is "low speed" depends on the particular object. What is low speed for a cannon ball is not low speed for a feather.
Title: Re: What is free fall?
Post by: Aemilius on 04/12/2013 19:02:54
Is air/wind resistance a component of free fall?  It is negligible at low speeds, but can be significant as one reaches terminal velocity.
It's wrong to say that It is negligible at low speeds because what is "low speed" depends on the particular object.

That's incorrect. It's not at all wrong to say that it's negligible in this case. As Mr.Calverd pointed out earlier (and I would have to agree), for an object like the 100 pound weight depicted in the animations falling through air a distance of 15 feet "....you would find it difficult to measure the difference between in vacuo and in air arrival times." This is, if I'm not mistaken or taking it out of context, the very definition of "negligible".


What is low speed for a cannon ball is not low speed for a feather.

That depends. In air or in vacuo? In air yes but in vacuo no. Again, as Mr. Calverd pointed out earlier (and again, I would have to agree), if I'm not mistaken or taking it out of context "....the mass of the objects is irrelevant (in vacuo). In free fall, all objects fall at the same rate."
Title: Re: What is free fall?
Post by: Aemilius on 04/12/2013 19:22:29
Very little pressure is required to blow out a building. If my "idealised shed" roof fell one third of the height of the building, the excess internal pressure would be over 700 lb per square foot. Windows - especially large ones - give way well below that level, and the rigidity of a modern bulding is partly conferred by the stressed skin window structure.

True, but really, when one reviews the video and graph concerning this particular building, it's glaringly apparent even to a layman that it went into free fall almost immediately, which would of course naturally rule out any bursting, or blowing out, due to a build up of air pressure in the lower part of the building some number of stories below (hidden from view).

In other words, it simply never had the chance to fall far enough before going into free fall for it to have plausibly developed the kind of pressure build up that could blow out 8 stories of glass, columns, etc. of the building.... Do you think we can we agree on that?         

Once a couple of steel uprights have buckled, the stress on the remainder is no longer compressive but rotational, and they aren't good at sustaining a rotational load.

I hadn't thought of that.... but then, as I study the symmetry of the facades descent, as a whole, while considering the over 300 foot wide (largest visible) facade particularly, I'm unable to model a progessive structural failure and subsequent collapse anything like that shown in the video....
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F06c559cd5c8a1df0aa4d57e1ed06ff51.gif&hash=6240b1956053c5906a144e94d36d2f9e)
....or anything remotely corresponding to the NIST graph, as it would require a novel horizontal "Newtons cradle" type of transfer of vertical load forces....
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Ffe40d9fc382b795e8c3a0d4746fda087.gif&hash=4f6b012863679c6b99039997d93ba996)
....to effect a progressive failure of the thirty columns supporting the two visible surfaces, or facades, of the building simultaneously....
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fc763491253f954e338cffd8d31c5e86d.gif&hash=830a3fa1791032a5153047ff669460fe)
....and even if I could manage that, the mystery of free fall remains.
 
"Google" has been unrewarding.... Is there any known precedent setting mechanism you're aware of?   

It looks very much as though the video'd building was also minimally rigid.

Hah! To your Ph.D., Mr. Calverd, you may now feel free to add a Masters Degree in understatement!
Title: Re: What is free fall?
Post by: alancalverd on 04/12/2013 20:09:05
No, it's not glaringly apparent!

The NIST graph shows velocity, not height, versus time. As Evan pointed out, free(ish) fall produces a linear increase of velocity with time, and this is only apparent after the first 2 seconds of collapse, which is consistent with my aerostatic model of lower-floor blowout. 

If the building was entirely supported by the internal steels, it would be surprising that none of them is visible  after the collapse. But half of the static load was borne by the outer steels, as in a conventional brick building. No great surprise there, you can use a steel web, with concrete, brick or steel panel infills for sway rigidity - same problem: it can burst and collapse very quickly from internal pressure.
Title: Re: What is free fall?
Post by: Pmb on 04/12/2013 22:01:07
Quote from: Aemilius
That's incorrect.
Nope. In fact it's very correct.

Quote from: Aemilius
It's not at all wrong to say that it's negligible in this case.
You donít seem to have read my post very carefully. I said that you canít talk about what is low speed in all generality because what works in one case doesnít work in all cases.

Quote from: Aemilius
That depends. In air or in vacuo?
Please go back and read my post again. This time please read it very carefully and to what I was responding to. I was responding to the following statement

Quote from: CliffordK
Is air/wind resistance a component of free fall?  It is negligible at low speeds, but can be significant as one reaches terminal velocity.
Since it was this comment which I quoted it means that it was this comment I was referring to. This comment is about falling in an atmosphere where there is air resistance acting on it. He made this comment without referring to what the object was and what is low speed and can be ignored for one object does not hold for all objects. When there is no resistance then the body is truly in free-fall.

By the way, since Iíve been a physicist for over a quarter of a century you donít have to remind me that all objects fall at a rate in a vacuum which is independent of their mass. However in general relativity (GR) the rate at which something fall does depend on the velocity its moving with, i.e. the gravitational acceleration is velocity dependant. See http://home.comcast.net/~peter.m.brown/gr/grav_force.htm

If the bodyís spatial extension is large compared to the region over which tidal forces canít be ignored then tidal forces will affect the bodyís rate of fall. I.e. in a curved spacetime large objects donít move on geodesics.
Title: Re: What is free fall?
Post by: alancalverd on 05/12/2013 00:13:28
Something of a circular argument developing here. "Low speed" is presumably any speed at which the acceleration of the falling object is for practical purposes indistinguishable from its value in vacuo, and will obviously be different for a sycamore piano or a sycamore seed. We dealt with form factors (though admittedly not autorotational lift) several pages ago, and it turns out that the questioner was specifically interested in concrete buildings falling down on the earth's surface. Even an old pedant like me thinks that we can ignore relativistic corrections when trying to work out why the building collapsed. 
Title: Re: What is free fall?
Post by: Pmb on 05/12/2013 01:18:59
Quote from: alancalverd
"Low speed" is presumably any speed at which the acceleration of the falling object is for practical purposes indistinguishable from its value in vacuo, and will obviously be different for a sycamore piano or a sycamore seed.
I was trying to make the point that "low speed" was not an absolute but relevant to the particular scenario. The way he said it seemed to me that he was speaking in absolute terms. Let's leave it at that and not pit pick, shall we?

Quote from: alancalverd
Even an old pedant like me thinks that we can ignore relativistic corrections when trying to work out why the building collapsed
I never mentioned a falling building. I was talking strictly about the statement In free fall, all objects fall at the same rate. and while true in Newtonian mechanics its not precisely true since GR has a correction for high speed motion. I'm not interested in whether you think I should make this point or not. It's a fact and we can't nor shouldn't say what people want to know.
Title: Re: What is free fall?
Post by: Aemilius on 05/12/2013 01:31:34
Right.... sorry about all that Pmb. Thanks for the input (I need all the help I can get!).
Title: Re: What is free fall?
Post by: Pmb on 05/12/2013 01:39:58
Right.... sorry about all that Pmb. Thanks for the input (I need all the help I can get!).
You're most welcome, sir! I was and will assume that you want to know as much as you can about this even when I know there's things you might have the knowledge to inquire about such as the corrections GR has to high speed free-falling like that around a black hole.
Title: Re: What is free fall?
Post by: Aemilius on 05/12/2013 01:49:09
Are you a Ph.D too Pmb? You've both given me something to think about. What do you think of alancalverds aerostatic model of lower-floor blowout? I've read a number of theories about how this building collapsed, but this is the first I've heard of it.

Just a note to add that it was a steel frame building, not concrete Mr. Calverd.... wasn't sure if I'd mentioned that.   
 
Title: Re: What is free fall?
Post by: Pmb on 05/12/2013 02:55:00
Quote from: Aemilius
Are you a Ph.D. too Pmb?
Not yet. I started working on it but had to stop due to an illness in the family. I plan on going back to graduate school next fall. I have the equivalence of a masters degree in physics.

Quote from: Aemilius
You've both given me something to think about. What do you think of alancalverds aerostatic model of lower-floor blowout?
I never saw it. He's in my ignore list for reasons I won't get into in open forum.
Title: Re: What is free fall?
Post by: evan_au on 05/12/2013 10:48:11
Just noticed your "Profile". Telecommunications.... Electrical Engineer?
Yes, my formal education was in Electrical Engineering.
Title: Re: What is free fall?
Post by: alancalverd on 05/12/2013 19:17:44
Just a note to add that it was a steel frame building, not concrete Mr. Calverd.... wasn't sure if I'd mentioned that.   
 

Steel frame, certainly, but apparently clad with concrete panels or something similar. Indeed a "concrete" building is essentially a combination of steel mesh to support tension loads and concrete in compression. A framework of rectangular steel lattice is not rigid. You need to brace it with triangulating beams (as in a bridge or a roof) or fill the spaces with panels made from something fairly incompressible like concrete - the usual procedure for large office blocks. Now if you blow out a few of those panels, the steels either side can buckle and the whole lot will collapse - as it did.
Title: Re: What is free fall?
Post by: Aemilius on 05/12/2013 19:37:07
Hi Mr. Calverd....

The NIST graph shows velocity, not height, versus time. As Evan pointed out, free(ish) fall produces a linear increase of velocity with time, and this is only apparent after the first 2 seconds of collapse, which is consistent with my aerostatic model of lower-floor blowout.

I understand.... It's actually a pretty cool theory. Like I said I thought I'd seen them all. So in your theory, it would be in the first seconds 1 and 2 (approx.) that the building descended to one degree or another and a rapid pressure build up occurred as a result. Then in the next seconds 3 and 4 (approx.) the actual period of free fall following the blow out event occurs....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F1aa684390441cf1c0b84565972a0b4ff.gif&hash=c337375f3fb6c2f398d316a2557a32d9)

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F007d76132c78aa42646407abccde7fd7.gif&hash=852d1fd68c344166fe910f6d0aa56d1e)

Am I close?
Title: Re: What is free fall?
Post by: alancalverd on 05/12/2013 20:23:40
It certainly consists with the video and graph, and also explains why the graph turns over at the top. At some point the descending piston will be travelling faster than the air beneath can escape, so it slows down a bit until there is enough pressure to cause another blowout - and of course it's now falling through rubble as well as air. 
Title: Re: What is free fall?
Post by: Aemilius on 05/12/2013 22:25:49
Hey evan_au....

Electrical engineering, interesting. So, about the aerostatic model of lower-floor blowout (replies 58 and 68).... What do you think?
Title: Re: What is free fall?
Post by: Aemilius on 07/12/2013 03:25:19
So I still can't quite get the aerostatic blowout model to work.

The collapse of the "Penthouse", on the left, is the first sign (below) of any catastrophic progressive structural failure....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fs16.postimg.org%2Flq2w3hx0j%2Fwtc7cbs5nk0.gif&hash=64badac13ccf97418ef2389219bf5ed5)

The rest of the rooftop structure to the right of the now collapsed "Penthouse" atop the building, however, remains stationary for about 4 seconds, and then it (the remaining rooftop structure) suddenly begins to descend largely intact, meaning the core columns must all have given way almost simultaneously (the dreaded horizontal "Newtons cradle" effect). As the remaining rooftop structure begins to descend, even before it reaches the roofline, the roofline also begins to descend, also largely intact, and they're seen afterwards essentially descending (below) together into the free fall period .....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fs4.postimg.org%2Ff14ewpy3f%2Fwtc7_cbs_lowman.gif&hash=70797d45b4ddd52f66bbfaba1c5e5288)

So.... How could the brief 30 to 35 foot drop of the remaining rooftop structure on the right have developed the kind of pressure that would blow out 8 stories of glass, cladding and steel columns many stories below?

The initial collapse of the "Penthouse" above column 79 (on the left) couldn't have built up pressure to the point of being able to blow out 8 stories about the girth of the lower part of the building (required for the observed period of free fall) because the facade continues to stand afterwards for about 4 seconds.

If the symmetry of descent and free fall for 8 stories, or over 100 feet, of the building is to be explained by a symmetrical blowout about the girth of the building, it obviously can't have occurred prior to the blowout. In other words.... While the initial symmetrical descent can explain an eventual blowout, an eventual blowout cannot explain the initial symmetrical descent, which leaves unanswered the original question as to how any initial symmetrical descent could have started to begin with (the dreaded horizontal "Newtons cradle" effect).

Otherwise, if there were to be a blowout event, I would expect increasing pressure to find and then cause to burst only the weakest part of the facade as just part of a larger overall conventional progressive structural failure....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Ffe9d14af1d06311c664208ec6584b0b1.gif&hash=f488b22a600d56f6e6df0781a8505b15)

The debris field surrounding the post collapse zone doesn't reflect what one would expect to see from a blowout event of that magnitude (spanning 8 stories about the girth of the building) either....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F007d76132c78aa42646407abccde7fd7.gif&hash=852d1fd68c344166fe910f6d0aa56d1e)

If pressure had built up sufficiently to blow out all the glass, cladding and perimeter columns at once over a span of 8 stories (over 100 feet) we should expect to find a more substantial debris field, certainly greater than the reported 70 feet in any direction....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Ffcd210fb67ca9c760a3b6ccf96064455.gif&hash=91651c17efaab35b61a9ba9e2149e4d6)


....and the way the walls all seem to have fallen inward rather than having been blown outward (notice the undamaged dust covered windows of a neighboring building)....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F92e5fdc3c3b8de1a62415c2467e30ad6.gif&hash=c2a2646803636d00a0072b3bd9875408)

....and finally, as you noted earlier, "Very few buildings (apart from nuclear power stations and the like) are designed to withstand outward force." So, this obviously wouldn't be the expected post blowout/collapse appearance of a debris pile resulting from that scenario. I couldn't go with the aerostatic blow out model/theory of collapse at this point.

Thanks again Mr. Calverd, it's been very interesting..... I'll let you guys have the last word. Looking forward to chatting with you now and again about other things.
Title: Re: What is free fall?
Post by: alancalverd on 07/12/2013 12:42:04
If you look carefully at the part just below the penthouse you can see the initial blowout happening about 5 floors below, and you can see the pressure wave propagating downwards and to the right. Now you have not only the roof but some 5 to 8 concrete floors descending as a piston so you don't need a lot of initial blowout to weaken the entire structure. As the collapse progresses, there will be an inward rush of wind behind the descending piston, so a fair quantity of outer wall debris will end up inside or close to the footprint of the original building.

The pressure wave doesn't have to propel the walls very far - a few feet will be enough to relieve the pressure but destroy the integrity of the structure.
Title: Re: What is free fall?
Post by: Aemilius on 08/12/2013 00:18:01

Is this what you're referring to Mr. Calverd?

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fs16.postimg.org%2Flq2w3hx0j%2Fwtc7cbs5nk0.gif&hash=64badac13ccf97418ef2389219bf5ed5)
Title: Re: What is free fall?
Post by: alancalverd on 09/12/2013 18:01:46
Indeed.
Title: Re: What is free fall?
Post by: Aemilius on 10/12/2013 19:05:59
Hi Mr. Calverd....

So, let me see if I really understand your aerostatic blowout model....
 
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F94c8bfd03987af73e015615957bcc375.gif&hash=a529788ef13d38e6b096c4ec3954f61a)

The building has been damaged (the 12 columns toward the rear) and there are several fires continuing to burn on various floors, but it's still standing....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F8a6ea4c53b69d635e14be3bea385e08f.gif&hash=5230bf753d60820f73b9074a3f382181)

In the first visible stage of the collapse, column 79 (circled) weakens and buckles due to heating from one of the fires. The other 5 columns supporting the West Penthouse immediately follow, buckling/failing in rapid succession, leading to the collapse of the West Penthouse into the building....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F6e477fb2300e15e380f2dbdcf1705d3d.gif&hash=83af9029297ed9879284db3ddc4cb1f8)

For about the next 4 seconds, though nothing much appears to be happening from the outside, on the inside the West Penthouse is actually continuing to crash its way downward like a giant piston through floor after floor gaining both mass and momentum as it goes, and this leads to a sudden rapid aerostatic pressure build up in the lower part of the building (out of view)....
 
 
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fc95dac06bec34c09b33c8f3f72a718d4.gif&hash=155da865ce9c4a30ee2facf35e637213)

In the next visible stage of the collapse, as the West Penthouse continues to descend, the aerostatic pressure becomes great enough that a catastrophic bursting, spanning about 8 stories, in the lower part of the building (out of view) begins, starting with the core columns, and it literally blows them away, leading to the beginning of the collapse of the East Penthouse into the building....
   
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F2670dbe85d1eee979f536f82612aade3.gif&hash=a24d3702dce7bf879cfa4d419c43d650)

As the bursting process continues, all the connections between the outer structure and the collapsing core columns are quickly severed by the sudden removal of 8 stories of core support. As a result, all at once within a second of the beginning of the descent of the East Penthouse, 8 stories of perimeter columns, cladding, glass and other materials making up the walls, unable any longer to withstand the increasing pressure and no longer restrained by any connections to the core suddenly expands and blows out, and it's this completion of a symmetrical blowout that breaks up/removes any remaining intact supporting perimeter columns, along with trusses, girders and other structural components, including interior/exterior walls, cladding, glass and other materials of the lower part of the building (out of view)....
 
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fceebf230f1c99631689a5e7de92d35dd.gif&hash=9601db96413ac2317bd707a5f8dabb06)

Finally, in the last visible stage of the collapse, all the various structural components that might have resisted the descent of the upper part of the building have been thoroughly dismantled/largely removed by the completed blowout, allowing the upper part of the building to quite naturally go into free fall for about 8 stories with no apparent resistance from either the core columns or perimeter columns as they had already been largely dismantled/removed by the blowout.... Is that close?
Title: Re: What is free fall?
Post by: alancalverd on 10/12/2013 20:07:10
You can't analytically separate the columns of a completed building from each other, the cladding, or the floors. The whole thing is designed to be just adequately rigid. If you blow out the cladding it will buckle some of the exterior columns to which it is attached, at which point the outer edge of the floor will fall, thus twisting the inner columns (because the concrete floors are floated on steel crossmembers bonded to the columns) . Steel columns are rigid in compression or tension, but not designed to withstand much torsion, and once buckled, they will collapse under their design compression load.

You can see the bursting on the video in your previous post. As the penthouse begins to fall, the texture of the face of the building changes as the windows bulge. The "texture wave" actually begins  fairly near the top and moves sideways (left to right) possibly quicker than downwards because corridors allow the air to move horizontally but the floors impede vertical propagation of the pressure wave.  If the building had a large atrium or substantial service shafts, this would allow quicker vertical propagation.

Remember that it isn't necessary to "blow away" the lower parts, only to get them to move outwards a couple of feet.     
Title: Re: What is free fall?
Post by: Aemilius on 10/12/2013 20:25:42
So the failure was all due to buckling.... None of the columns were actually blown away?
Title: Re: What is free fall?
Post by: alancalverd on 10/12/2013 23:21:51
Try sitting on a corrugated cardboard box, then get someone to kick the side of the box! Minimally stiff structures live up to their name.
Title: Re: What is free fall?
Post by: Aemilius on 12/12/2013 10:19:27
So, none of the columns would have actually been blown away by the explosive pressure that had built up.... but some of the columns would certainly have been weakened and buckled by the blowout.
Title: Re: What is free fall?
Post by: alancalverd on 12/12/2013 11:32:49
Pretty much the point. Once one column has buckled, the weight of the floor around it and all the structure above and outside it will exert a torque on the neighbouring columns  and they will begin to bend. As soon as the next one has gone beyond its elastic limit you will have more floor area exerting torque on the next nearest neighbours....Hence the gentle initial acceleration building to near-free fall.

It's a mistake to think of modern buildings as composed of independently stable parts - the whole structure is only rigid if it retains full integrity. There were several instances of half-built "box girder" bridges collapsing in the Sixties: these structures were brilliant on paper and in the laboratory but only met their design strengths when complete - which by definition doesn't happen on a building site until the last day. And like office blocks, they were also vulnerable to serious weakening through minor damage. We live with stressed-skin aeroplanes and racing cars because they can be inspected easily, withdrawn from service if damaged, and repaired under non-stress conditions, but civil structures can't.   
Title: Re: What is free fall?
Post by: Aemilius on 17/12/2013 00:06:43
Cool theory, but it doesn't add up. It seems to me that for your "aerostatic blowout" model to work here it would have to take into account how all the remaining perimeter and core columns could all have essentially failed at once (starting with the descent of the East Penthouse), rather than progressively like the scenario described above, over a span of about 8 stories in order to match the conditions that we know must have, or very nearly must have existed....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F5a99bad2e9493e6d02f70da3fbda4d89.gif&hash=08f03bbad4f7ea8d7a4f52b0a0466e46)

....beneath the falling visible part of the building during its observed descent at gravitational acceleration for 105 feet in 2.25 seconds....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F0d8f489c42d14f50777e0d8e90059b6a.gif&hash=ec7e55896d81c088b4e19d42f480a2bb)

The shockwave/air blast in your model that would have been created by the initial collapse of the West Penthouse within the building by the "piston effect" would not have been powerful enough (left) to account for the creation of those conditions (center), and even if it was powerful enough to have blown out all the cladding and windows and buckle all the remaining perimeter and core columns too (right), which I very much doubt it would have been powerful enough to do, the building still wouldn't have gone into free fall....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Ff24d4093dd7e5ed00a0fdba686ee42a3.gif&hash=e80805776247ac4ef83ef741b49df33d)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fcbd066d27eeaed9412d495b324a0a186.gif&hash=4c84ab5e173e8a3918e4aafa4eb163b8)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F115c6d9b36148d757137463278611934.gif&hash=32bbb1986275f07e77064f9c1a5d4a31)

Buckling columns don't just go from a hundred percent to zero percent when they buckle, they go from a hundred percent to zero percent while they buckle and that takes time. Whether one column or a hundred, no free fall....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2Ff2176b9174d6af03e8c18ccb0ac38867.gif&hash=21ef95bd467d5e2ac03b2f5df212d189)
Control on the right, details....
http://picasion.com/pic76/ef2992a1bed34a1ad9d2e8f520c5ad7e.gif
Title: Re: What is free fall?
Post by: alancalverd on 17/12/2013 16:22:25
Have it your way if you wish - magic?

The rate of stress propagation throughout the structure is the speed of sound, which in steel or concrete is 5 to 7 times its speed in air - about 1 mile per second. And remember that the video does not show immediate free fall but quite slow acceleration in the initial few seconds.
Title: Re: What is free fall?
Post by: Aemilius on 18/12/2013 16:45:37
Have it your way if you wish - magic?

The rate of stress propagation throughout the structure is the speed of sound, which in steel or concrete is 5 to 7 times its speed in air - about 1 mile per second.

Right. Looks like you found a novel (if highly improbable) "Newtons cradle" effect to explain the failure/buckling of so many columns at once. Again though, even if that were possible the buckling of all the columns at once will still not result in free fall....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F27116a12288329cea1fc0a4cf817d33a.gif&hash=4e000b6b63270f88bef96ec2b5f050a9)

And remember that the video does not show immediate free fall but quite slow acceleration in the initial few seconds.

The initial few seconds? Unless I'm interpreting this improperly, it's not a "few seconds" but only about 1.75 seconds from the beginning of the descent of the East Penthouse to the entire building going into free fall like a rock being dropped off a cliff....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F6c7cd2005f1c75d081a720e434c5c713.gif&hash=9d9ca0a5d356910efead1c858dd2d6ca)

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F1aa684390441cf1c0b84565972a0b4ff.gif&hash=c337375f3fb6c2f398d316a2557a32d9)

Anyway it wouldn't be when it went into free fall that's amazing, what's amazing is that it went into free fall at all. For example.... Is there some point during this collapse (below right) where one could say "The columns have all clearly buckled and the level of resistance offered by them to the upper part of the building that's descending should be roughly equivalent to that of air (below left) at this point in the collapse."....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fa0cb7908dee38177e36e60b0cc7d95f6.gif&hash=6f33a99ca916bcba11db979a8f8cf484)

I don't think the progressive collapse of a building (below right) can achieve gravitational acceleration (below left) over time through the path of greatest resistance in a manner indistinguishable from air.... Is there an equation that describes how that would work?

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F5b9c4cc103d2e6272956c87cf5443cf1.gif&hash=cc9d28a4653da9a26d8b59eadb9c9e04)
   

Thanks again for responding Mr. Calverd.
Title: Re: What is free fall?
Post by: Aemilius on 19/12/2013 04:46:48
The rate of stress propagation throughout the structure is the speed of sound, which in steel or concrete is 5 to 7 times its speed in air - about 1 mile per second. And remember that the video does not show immediate free fall but quite slow acceleration in the initial few seconds.

Just thinking that's interesting. I was aware of the speed of sound in steel being greater than the speed of sound in air, but.... Stress propagation? Does that mean that if one bends a 5 foot long iron bar at one end that the other end will undergo some measurable similar type of stress a fraction of a second later? Maybe I'm not clear on the definition of "stress propagation".... Is that seen by physicists as being essentially synonymous with "sound propagation"?
Title: Re: What is free fall?
Post by: alancalverd on 19/12/2013 18:48:41
The cross bracing and floor reinforcements of a modern building are such that there may be several "rigid" paths, allowing stress to be propagated by tension and compression, between any two points. Tension and compression forces are transmitted at the speed of sound - by definition.

Imagine a simple cubical box frame. It has tension and compression rigidity along the axes of the struts but is very weak in shear and torsion. So we add diagonal tensioners, or fill the faces with compressively rigid panels, and now any force applied to a corner will be transmitted rapidly to all the others.   

Bending a single bar beyond its elastic limit at one point won't transmit much stress to the other end, but in a real building the ends are connected  by a whole lot of other bits of rigid structure. Hence you have to look at your collapsing building as an entity, not a bunch of disconnected components.
Title: Re: What is free fall?
Post by: Aemilius on 19/12/2013 20:38:35
Thanks Mr. Calverd.... understood.
Title: Re: What is free fall?
Post by: Aemilius on 21/12/2013 06:14:48
Hi Mr. Calverd. As you outlined earlier....

Once one column has buckled, the weight of the floor around it and all the structure above and outside it will exert a torque on the neighbouring columns  and they will begin to bend. As soon as the next one has gone beyond its elastic limit you will have more floor area exerting torque on the next nearest neighbours....Hence the gentle initial acceleration building to near-free fall.

....in a progressive collapse due to buckling, the buckling of one column leads to the buckling of the next, and the buckling of that column leads to the buckling of the next and so on. In that scenario (starting with column 79 which would be on the left) we should, at least to some degree, expect to see some recognizable signature of that failure mode during the collapse. It should have progressed across the 300 foot wide facade of the building from left to right during the buildings descent, but we don't see anything like that. Buckling can't account for how the conditions required for free fall that we know must have existed, or very nearly existed, could have arisen beneath the visible upper part of the building as it descended either. That scenario doesn't match observations....

Post blowout (slower than free fall) progressive column
failure due to buckling.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F06c559cd5c8a1df0aa4d57e1ed06ff51.gif&hash=6240b1956053c5906a144e94d36d2f9e)

The rate of stress propagation throughout the structure is the speed of sound, which in steel or concrete is 5 to 7 times its speed in air - about 1 mile per second.


With the "speed of sound stress propagation" approach, by which (theoretically) all the remaining columns throughout the building could've been buckled at roughly the same time following the buckling of column 79 and subsequent collapse of the West Penthouse, any "aerostatic shockwave" that resulted, just as with the first scenario, would only result in buckling at best which, though it may account to some extent for the initial uniform descent of the facade, again, doesn't account for the conditions required for free fall we know must have existed, or very nearly existed, or how those conditions could have arisen beneath the visible descending upper part of the building....

Post blowout (slower than free fall) simultaneous
column failure due to buckling.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F9c68e547d22a337a9448b8c21d55fe12.gif&hash=659787a1a046bcc5f442d8431ed9efd8)
 
In neither of those scenarios (or any scenario that only buckles the columns) would an aerostatic blowout have been powerful enough to have physically blown out all the remaining columns, and since they could at best only have caused the columns to buckle, knowing as we do that buckling columns cannot give rise to or match the conditions required for free fall to occur....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F8db27a83092f9cb1be47bba39ea92628.gif&hash=70fde890e8f9091743cb39d2faa91d2d)


....neither the mechanism of buckling nor the outcome predicted by it can in any way account for or explain the prevailing conditions we know the upper part of the building must have fallen under....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F0d8f489c42d14f50777e0d8e90059b6a.gif&hash=ec7e55896d81c088b4e19d42f480a2bb)

In other words, it's inconsistent with the observation of free fall since we know buckling cannot give rise to the conditions required for free fall to occur, so the "areostatic blowout" model for how the building came down fails.

Nice try though!
Title: Re: What is free fall?
Post by: alancalverd on 22/12/2013 16:11:42
Quote
the initial uniform descent of the facade,

not seen on the video. You can see the propagation of a shockwave diagonally across the front of the building and the roof accelerates up to near-free-fall for several seconds. The acceleration only decreases when the collapse is almost complete.

My concern is that you are unlikely to accept any explanation other than the sudden magical and simultaneous disappearance of all the steelwork, which would be a proud first for the demolition industry, especially if it rematerialised on the far side of the moon.
Title: Re: What is free fall?
Post by: Aemilius on 23/12/2013 01:07:13
You can see the propagation of a shockwave diagonally across the front of the building and the roof accelerates up to near-free-fall for several seconds. The acceleration only decreases when the collapse is almost complete.

A moot point. Your catastrophic aerostatic blowout/speed of sound stress propagation shockwave (really reads more like it was hit by an asteroid!), as we discussed earlier, could have only buckled some of the columns, and even had it been powerful enough to buckle all the remaining columns, knowing as we do that buckled/buckling columns, whether weakened by heat (left) or by overloading (right), whether buckled in sequence or simultaneously, whether one or a hundred....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F171da9bd639a474f93f75416474f53ce.gif&hash=85cbc019fdd604418c2f91dfb5ef006e)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fa338ba3cef6cdac0cc13fe19a7c5c2bc.gif&hash=74af5a6ed9dfd9e898acf549f989cd15)
Control on the right, details....
http://picasion.com/pic76/ef2992a1bed34a1ad9d2e8f520c5ad7e.gif

....cannot give rise to or match in any way the conditions required for the observed period of free fall the building verifiably underwent. In other words, whatever this "shockwave" did, it couldn't have created the required conditions for gravitational acceleration "The condition under which a body is, literally, free to fall under the influence of the local gravitational field with no resistance to its acceleration."

The model still fails.

My overall impression (not trying to be rude) is that somehow you'd like to minimize the significance of free fall by referring to it as "near-free-fall" and similar, maximize the impression of suddenness of some modes of failure that can "come down very quickly" and emphasize the inherent lack of structural integrity/flimsiness of construction in this case but, except for progressive structural failure involving things like bridges that pass through the air over rivers and such, you'll not succeed at marrying progressive structural failure of any building to gravitational acceleration.... if I'm not mistaken, it's right up there with perpetual motion. Haven't you some equation or formula that would bear any of this out?
Title: Re: What is free fall?
Post by: alancalverd on 23/12/2013 17:10:40
Nothing moot about it: the evidence is all on the video - or was that a fake?  Anyway here are the relevant equations

a = F/m  (Newton's Law, where F is the net force)

F -> mg (= GmM/r2) as the supporting structure fails in vacuo.

v = u + integral(at)dt  at any time

These equations describe the observed speed/time curve quite nicely. You can't "minimise the significance of free fall" because the curve pretty closely approximates to free fall over most of its length.

What, apart from structural failure and gravity, do you think could cause a structure to collapse at a rate approximating to free fall, apparently without damaging adjacent structures.? A giant vacuum cleaner, perhaps? 
Title: Re: What is free fall?
Post by: Aemilius on 24/12/2013 07:15:51
My concern is that you are unlikely to accept any explanation other than the sudden magical and simultaneous disappearance of all the steelwork, which would be a proud first for the demolition industry, especially if it rematerialised on the far side of the moon.

Any explanation? We've only discussed one theory so far Mr. Calverd, yours, so I'm not sure how your "concerns" made it all the way out there into left field. If it was magic I was looking for though, I would have instantly accepted your catastrophic aerostatic blowout/speed of sound stress propagation shockwave model.... it's a beauty!

Nothing moot about it: the evidence is all on the video - or was that a fake?

Your model only buckles the columns, and since we know buckled/buckling columns can't account for or explain the creation of the conditions required for free fall, it's moot. You can buckle all the columns on every floor of the building at the speed of light if you wish.... no free fall. You must know this. 

Anyway here are the relevant equations

a = F/m  (Newton's Law, where F is the net force)

F -> mg (= GmM/r2) as the supporting structure fails in vacuo.

v = u + integral(at)dt  at any time

These equations describe the observed speed/time curve quite nicely. You can't "minimise the significance of free fall" because the curve pretty closely approximates to free fall over most of its length.

I get the free fall part. What I was really asking you for is some hypothetical scenario with a formula or equation, even a crude graph, anything that describes how any falling object, with a starting velocity of 0, could gently accelerate building to free fall speed while overcoming resistance in the process. For example.... How long would it take a 100 pound cannon ball dropped from a height of 1000 feet (with a starting velocity of 0) working against a resistance of 10 pounds to achieve (in vacuo if you prefer) gravitational acceleration? 

What, apart from structural failure and gravity, do you think could cause a structure to collapse at a rate approximating to free fall, apparently without damaging adjacent structures.? A giant vacuum cleaner, perhaps?

What apart from structural failure and gravity? My impression is that you're still including/considering gravity driven progressive structural failure as something that might be able to explain this.... it can't. There is no gravity driven progressive structural failure mode that can result in gravitational acceleration (except for bridges and other structures that pass through air), so I don't know. The only model I've seen so far that really displays a solid one to one behavioural correspondence with the video evidence is closer to your "brick shed gas explosion near the base of the structure", which you only touched on briefly. 

Originally the idea was to firmly establish what the conditions are that govern free fall and you did that.... "The condition under which a body is, literally, free to fall under the influence of the local gravitational field with no resistance to its acceleration."....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F78fe757793d30a322732edd16cff4bde.gif&hash=3b38c60fdf117bb618d90bba83f4e460)

We agreed that this (below) was a fairly accurate and reliable empirical method of determining, by comparing distance travelled and rate of descent of the red marker with a control, that the scenario weight must have fallen under free fall conditions (nothing beneath it) despite not being able to see into the space it was falling through....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F1036ed956866bb76e5e518d9c4e7a69c.gif&hash=ab9cc405b00f82c449c66b34fcc956cf)
Control on the right, details....
http://picasion.com/pic76/ef2992a1bed34a1ad9d2e8f520c5ad7e.gif

....which naturally led to the comparison....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F0d8f489c42d14f50777e0d8e90059b6a.gif&hash=ec7e55896d81c088b4e19d42f480a2bb)


.... establishing the conditions (nothing beneath it) under which the visible upper part of the building must have fallen....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F5a99bad2e9493e6d02f70da3fbda4d89.gif&hash=08f03bbad4f7ea8d7a4f52b0a0466e46)

Now, you're asking me to believe that there are other conditions under which free fall can occur, and even suggesting that the two fall time scenarios below, under certain conditions, can actually be the same even though in the one scenario (left) there's considerable resistance/mass occupying the space beneath the falling object, and in the other scenario (right) there's nothing but air occupying the space beneath the falling object....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2Fdfaeebd52d3988a358bda489db327ae5.gif&hash=b86170a798cda6f934c5b816ec790707)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F25f01288133a43b706e7b7c7ef6a1cc1.gif&hash=d53a787bbf12ecf712597d0806820f1c)

Even after agreeing about the improbability of your catastrophic aerostatic blowout/speed of sound stress propagation shockwave being able to do anything more than buckle a few columns (or even all the columns, it makes no difference) you're continuing to insist that buckling, a mode of structural failure we know doesn't create the conditions for or result in free fall....
 
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2Ff2176b9174d6af03e8c18ccb0ac38867.gif&hash=21ef95bd467d5e2ac03b2f5df212d189)
Control on the right, details....
http://picasion.com/pic76/ef2992a1bed34a1ad9d2e8f520c5ad7e.gif

....somehow created the conditions for and resulted in free fall!

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fd5dbd5d68ab7326804067a722fe8bc06.gif&hash=7e70d6df2ef33d054d6de5f31e816578)
Control on the right, details....
http://picasion.com/pic76/ef2992a1bed34a1ad9d2e8f520c5ad7e.gif

Abracadabra.... Mr. Calverd.
Title: Re: What is free fall?
Post by: alancalverd on 24/12/2013 09:45:42
Quote
I get the free fall part. What I was really asking you for is some hypothetical scenario with a formula or equation, even a crude graph, anything that describes how any falling object, with a starting velocity of 0, could gently accelerate building to free fall speed* while overcoming resistance in the process. For example.... How long would it take a 100 pound cannon ball dropped from a height of 1000 feet (with a starting velocity of 0) working against a resistance of 10 pounds to achieve (in vacuo if you prefer) gravitational acceleration? 

It can't. If F = mg - f, the mass can never accelerate* at g.

But then it didn't, so what's the problem?

I was very careful always to state "near free fall" because there was obviously always some resistance. Not a lot, but if you calculate the slope of the linear part of the velocity/time graph very carefully you will find that it is a bit less than g, and turns over at the top as the falling roof approaches a terminal speed with increasing f.   

No need for a hypothetical scenario - this is how loaded minimally stiff structures collapse: slowly at first, then more rapidly up to terminal speed. Try it with a house of cards! 

*Remember that free fall isn't a speed but an acceleration.
Title: Re: What is free fall?
Post by: Aemilius on 24/12/2013 16:08:11
Thanks, my error.... meant to say acceleration not speed. 
Title: Re: What is free fall?
Post by: alancalverd on 24/12/2013 17:20:30
OK, so your cannon ball weighs 100 lb = mg  (if you use the proper Imperial system of units, this gives the mass m of the cannon ball as 100/g, about 3.5 slug)

Resistance = 10 lb

So the accelerating force is a constant 90 lb

So from the instant is is released, the cannon ball accelerates at a constant 0.9 g.

In order to accelerate slowly at first, then gradually more rapidly, you need to replace the constant retarding force with a gradually decreasing one. Pretty much what happened to the roof of the building, in fact. The initial retarding force was obviously sufficient to prevent the roof from collapsing since the structure was built, then a bit of the structure gave way, the roof began to move, and the supporting structure progressively disintegrated, allowing the roof to accelerate more rapidly towards g, limited by increasing aerodynamic drag until it reached terminal speed or hit the ground, whichever came first.
Title: Re: What is free fall?
Post by: Aemilius on 26/12/2013 18:36:34
Hi Mr. Calverd (hope you had a nice Christmas!)....

Your model seems to be growing more complicated, like a perpetual motion machine that really can work.... if we can just manage to add that one last gear!
 
Originally, we just had the brick shed "aerostatic blowout" gear to drive the whole thing, but when it came to light that the bursting event would not have been powerful enough to remove any of the columns creating the conditions required for free fall to occur, only buckling some of them at best....

The "speed of sound in steel stress propagation shockwave" gear is added to explain an even greater and more sudden weakening and subsequent near simultaneous buckling of all the columns, but when it came to light that even more forceful buckling of all the columns at once would not create the conditions required for free fall to occur....
 
"The roof began to move" gear is then added to explain how events occurring on the roof could have caused the columns to not only have buckled, but also to have "progressively disintegrated" (presumably fast enough to create the conditions required for free fall) 20 or more stories below where they would likely have been heavier and stronger....

And all of it, the whole "aerostatic blowout / speed of sound in steel stress propagation shockwave / roof began to move" contraption of catastrophic buildup of aerostatic pressure purportedly responsible for all this is powered by just the first 25 to 30 feet of descent of the West Penthouse, when as you say, the first evidence of a bursting event is seen along with an aerostatic shockwave texturally rippling across the buildings facade (apparently without much regard for any interior walls or flooring) along now with roof movement that purportedly causes immediate buckling and subsequent progressive disintegration (progressive disintegration?) of the columns many stories below....

It's almost as though you're attempting to conjure a nuclear explosion from a firecracker!
 
And we still have one more little gear left over that will help smooth things out.... We mustn't forget that the building was very badly designed (probably a junior architect at some nickle and dime outfit working out of a garage somewhere), and as anyone with eyes can see it was clearly a heavily loaded structure that was very poorly engineered and flimsily constructed (some say just barely able to stand!), and besides, free fall never really ocurred anyway making it all quite ordinary, so.... What is all the fuss about?
 
In a nutshell, the reason you're having to do all this is because of the inadequacy of the original precedent setting example you used for your model. The aerostatic blowout in the "brick shed" analogy, wherein an explosive aerostatic blowout following structural failure in the lower part of the walls can result in complete removal of support, allowing the structural components of the roof (without the shingles) to approximate free fall for a period of time under the conditions required for free fall to occur, ultimately couldn't be used to support an aerostatic blowout in the case of the building because, unlike the complete removal of support that could be expected to occur at some point in the case of the brick shed example, the same mechanism when applied to the building leaves the columns in place.... and you've been struggling with that ever since.
 
It is impossible for any period of free fall to occur in the case of the building in the same way it could be expected to occur in the case of the brick shed from an aerostatic blowout because the conditions required for free fall to occur are actually created at some point during the post blowout descent of the brick shed in the example, but the conditions required for free fall to occur are never actually created at any point during the post aerostatic blowout descent of the real building.
 
The aerostatic model fails.

I was very careful always to state "near free fall" because there was obviously always some resistance.

As far as whether or not it went into free fall, the NIST web page just says.... "Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall)" ....followed by.... "During Stage 2, the north face descended essentially in free fall, indicating negligible support from the structure below." I'm assuming they're as familiar with the precise use of language as you are so I'm going with that.

After your review of the graph though, how much less than g did you estimate it was.... Do you remember?
Title: Re: What is free fall?
Post by: alancalverd on 26/12/2013 23:25:55
Not sure what you are getting at here. On the one hand you say it is impossible to create the conditions for free fall, and on the other you are claiming that it was observed.

NIST was properly circumspect in its language   

Quote
descended essentially in free fall, indicating negligible support from the structure below."


Qualifying adjectives are not zeroes.

Far from adding gears (not the way to build a PM machine - simpler is better) I'm just trying to explain what you can see in the video, using known physics and engineering. A real building is a very complicated and interconnected structure so the best we can achieve from a blurred external video is bound to be an approximation, and the real thing will have a lot more hidden gears.

Difficult to estimate the actual acceleration from the image I have of the NIST graph. g is around 32.2 ft/sec2 and the maximum slope of the graph is certainly " a bit more than 30". I would be surprised if it exceeded 32, and the only way it could reach or exceed 32.2 would be if the air was being sucked out of the building. You could do that with an explosive but that would produce a different shockwave pattern from what we observe in the video.
Title: Re: What is free fall?
Post by: Aemilius on 26/12/2013 23:56:07
I didn't say it's impossible to create the conditions for free fall (the brick shed is a good example), what I said was it's impossible for any period of free fall to have occurred in the case of the building in the same way it could be expected to occur in the case of the brick shed example you've constructed your theory around because free fall was observed (during the descent of the building), and that since nowhere in the course of your model playing out would the conditions required for free fall to occur be created, your model fails.
Title: Re: What is free fall?
Post by: alancalverd on 27/12/2013 00:30:57
In what way? I haven't "constructed a theory around a brick shed" because we know that this was a steel frame building, and I've gone to a lot of trouble to explain how torsional stresses are incurred in a collapsing steel-and-concrete structure. The "brick shed blowout" is just a simple example of aerostatic collapse under an intact roof, which can result in loads beyond the design limit. A building with significant internal structure is bound to be a bit more complicated.

Nor have I criticised the design or construction of this building. "Just stiff" is optimal for civil structures and this one had presumably tolerated its design stresses of floor loading and windage. Building codes are particularly stringent with regard to fireproofing of steelwork precisely because it is prone to spectacular collapse under torsional load, which suggests that the initiating fire was particularly intense - sprinklers and passive protection should provide adequate time for evacuation under foreseeable conditions. 
Title: Re: What is free fall?
Post by: Aemilius on 27/12/2013 04:53:35
In what way? I haven't 'constructed a theory around a brick shed' because we know that this was a steel frame building...."

Maybe I misunderstood (shouldn't surprise anyone, I'm an eighth grade dropout!), but I got the strong impression, at least at the time, that in reply 68 where I described my interpretation of your theory in some detail, including a schematic animated representation that very much resembles the brick shed example....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F007d76132c78aa42646407abccde7fd7.gif&hash=852d1fd68c344166fe910f6d0aa56d1e)

....and judging by your affirmative response in reply 69, it looked like that was exactly what you had in mind and had originally constructed your theory around, you even mentioned it as such in connection with the NIST graph in reply 58 saying that it was "....consistent with my aerostatic model of lower-floor blowout."
 
Apologies though.... if I was mistaken.
Title: Re: What is free fall?
Post by: Aemilius on 28/12/2013 09:34:24
So.... Was I mistaken?

....I've gone to a lot of trouble to explain how torsional stresses are incurred in a collapsing steel-and-concrete structure.

And I really just want to say, once again, how much I appreciate your patience and the time you've taken to discuss it with me.... I'm very glad to have met you.

There are, however, other features of the aerostatic model that I see as being possibly/probably problematic though, aside from the obvious fact that the actual conditions required for free fall are never created in the course of this model playing out....

The "piston" effect....

The West Penthouse breaks in half immediately upon beginning its descent. I believe this would have largely negated the piston effect that must be relied on to explain a catastrophic build up of aerostatic pressure since the "piston", right from the start, falls in at least two pieces, so there wouldn't have been any kind of a "seal" there between the "piston" and the "cylinder wall" to fascilitate any aerostatic build up of pressure, and in addition to that, further on, there would have been nothing to prevent any aerostatic build up that did occur from simply venting in an upward direction out through the gaping hole left in the roof of the building after/as the volume of rubble that had made up the West Penthouse continued its descent within the building.
 
The "bursting"....

After reviewing the video multiple times, the evidence for an "aerostatic blowout" or "bursting" event that you point to in the video emerging from the facade at the far end of the building about five stories beneath the West Penthouse, amazingly, actually appears at almost the exact same time as the beginning of the descent of the West Penthouse itself. I believe this could explain windows being blown out on one or maybe two floors immediately below the penthouse, but it doesn't seem at all probable at that point, after just the first few feet of its descent, that the West Penthouse could possibly have developed enough aerostatic pressure within the building to have blown out even one window five stories below, let alone the cladding, after having only fallen such a short distance prior to the appearance of the purported "bursting" five stories below.

The "shockwave"....

The evidence for the "shockwave" that's seen texturally rippling accross the buildings facade, as with the "bursting" event, amazingly, also appears at almost the exact same time as the beginning of the descent of the West Penthouse itself, and again, just as with the "bursting" but even more so, it doesn't seem at all probable that, at that point in its descent, it could possibly have developed anywhere near the level of aerostatic pressure within the building that would be required to generate such powerful and wide spread effects, racing throughout the building and buckling columns as it reverberated throughout the 610 foot tall structure that covered an area greater than that of a football field. Although the windows are seen to shatter in a way that's suggestive of a "shockwave", inexplicably, there is no visible indication of any accompanying ejecta similar to the "bursting" event, no papers, no smoke, no dust.... nothing. The windows merely shatter which, to me, is really much more suggestive of a slight structural flexure having occurred as a result of the first violent initial moments of descent of the West Penthouse as it tore itself away from other structural components, thereby distorting the normal dimensions of the window frames and causing the windows to shatter progressively in rapid succession across the facade of the building, a process that would, like the "shockwave", also have continued for the entirety of the buildings descent, or until all the windows shattered.

Thanks again for your time and all your responses Mr. Calverd.
Title: Re: What is free fall?
Post by: Aemilius on 28/12/2013 20:55:20
Just a note to add that those are all just subjective debatable observations. The main objection that thoroughly deflates the aerostatic model is still that it badly fails to display a close enough behavioural correspondence to the confirmed observation of gravitational acceleration, since there is no point at which the conditions required for it to occur actually arise in the model as it plays out to completion. We could revisit the rest if/when that hurdle is behind us.
Title: Re: What is free fall?
Post by: alancalverd on 29/12/2013 01:05:55
Remember that you don't need spectacular ejecta to weaken the structure. A few extra pounds internal pressure per square foot of cladding is all that is required to destroy the lateral and torsional stiffness of the building. And in a tall modern building the windows are a significant contributor to the stiffness of the structure. 

More importantly, the collapse of the west penthouse isn't the cause of the failure but an early visible effect. You stated that the primary cause was a fire some way below, which presumably weakened some of the steel uprights. Once the steel starts to buckle at one point, the weight of all the floors above it starts to move downwards and between them they create quite a substantial piston. One foot of collapse will increase the air pressure by about 1 lb/sq ft in the storey immediately below. The problem is that you can't see the internal floors moving. 

And finally, aerostatic blowout doesn't cause collapse by taking away all the supporting structure. All it does is reduce the stiffness of the building, which then accelerates as seen.

Quite clearly the conditions do arise for near-g acceleration, and there is no evidence for a magical dematerialisation of the internal structure, so if you don't like the obvious mechanism I proposed, you will have to propose a better one! What do you suggest?
Title: Re: What is free fall?
Post by: Aemilius on 29/12/2013 02:01:00
Thank you Mr. Calverd, let me ruminate on all that for a bit. Before I forget though, just for the sake of clarity....

Was I mistaken or not (reply 99) as to what you originally constructed your theory/model around? 
Title: Re: What is free fall?
Post by: alancalverd on 29/12/2013 16:30:12
The key is in an earlier exchange, around 67 - 69, where I discussed the rigidity of a compound structure . A simple brick shed derives all its properties from the compressive strength of the brick shell, because there isn't anything else, so if you blow the bottom outwards it will collapse as a simple piston, but we are dealing here with multiple internal compartments and substantial intermediate loads in the form of concrete floors. The whole thing only works as a whole, so removing or weakening the exterior panels allows the stuff inside to collapse, particularly if the fire has been burning for long enough to weaken several interior uprights. The piston/blowout mechanism is the last straw that triggers the rapid phase of collapse, not the entire mechanism.
Title: Re: What is free fall?
Post by: Aemilius on 31/12/2013 20:05:08
So to review your theory....

Column 79 buckles due to heat.

Five other columns that, along with column 79, had supported the West Penthouse then buckle in rapid succession.

The now unsupported West Penthouse, together with at least the five or so floors immediately below it, begins to descend as a substantial "piston" causing a catastrophic build up of aerostatic pressure within the building below (even though it immediately breaks in half leaving a gaping hole in the roof which appears in the video to actually be venting pressure upward through the top of the roof)....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fs16.postimg.org%2Flq2w3hx0j%2Fwtc7cbs5nk0.gif&hash=64badac13ccf97418ef2389219bf5ed5)

At the same time as the West Penthouse is beginning to descend, it causes the roof to move, setting in motion a process that "progressively disintegrated" the support structure below (spontaneous catastrophic progressive structural disintegration.... a novel mode of structural failure?)....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F6feff1cd4625a93e2cd98e4a97cda712.gif&hash=ffd93b719d5954529ca0da3211f31c02)


Over the next four seconds or so the "piston", as it continues to descend, gives rise to multiple aerostatic blowouts (even though no multiple aerostatic blowouts are observed that indicate anything like that occurred) that further weaken the building by blowing out cladding and windows (even though no cladding or ejecta, spectacular or otherwise, are observed being blown out anywhere)....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fe7c961fb4327cc8a1b3beb310a7fa003.gif&hash=60412c4c06a5a92396f4f91847a6e9e6)


During the same four or so seconds, as the penthouse descends, multiple structurally transmitted stresses (generated by multiple aerostatic blowouts there's no evidence of) invisibly reverberating throughout the steel structure at the speed of sound quickly causes more columns to begin buckling elsewhere within the building....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fb2ba79541e97f5393f4e7ec84b68920d.gif&hash=daf37bef3d28b9c70bd104bbbf60825f)


Together, this constellation of contributing factors consisting of a progressive sequence of progressive failures occurring at various times and in different ways throughout the building ultimately ended up coming together to act in concert at some point, miraculously causing the 610 foot tall building to literally fall (right) for over 100 feet at gravitational acceleration straight down through itself as if in air (left) through the path of greatest resistance....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F8db27a83092f9cb1be47bba39ea92628.gif&hash=70fde890e8f9091743cb39d2faa91d2d)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F9fda7447ab53a056ff5f02c28634ecb3.gif&hash=d6fd60056393308da5bd58bb43bf64f0)
 
To more easily explain the acceleration of the descending upper part of the building to near-free-fall (it was, after all, only essentially free fall, not free fall, and there was always some negligible resistance that must be taken into account), we need only reverse what we have known for centuries about what actually happens during a real natural progressive structural failure so that resistance to the descending upper part of the building gradually decreases rather than gradually increasing as it actually would (increasing resistance invariably causes the descending part of any naturally collapsing structure, aside from bridges and other structures that pass through the air, to either just come to a halt, or come to a halt and then topple)....

There's no need for even cursory scenarios, analogies or any diagrams that would even begin to show how any of this could possibly happen either, because this is simply how loaded minimally stiff structures behave under these conditions (even though no similar incidents of any kind are cited or referred to that would in any way suggest anything of the sort).

It's clear that the conditions for near free fall arose (all the while remaining perfectly unclear as to exactly how the conditions required for even near-free-fall could possibly arise), and since there's no evidence of any magical dematerialization of supporting structure that rematerialized on the other side of the moon, if I don't like the obvious mechanism your proposing (which couldn't be any less obvious) I'll just have to come up with something better.
   
As far as coming up with something better goes Mr. Calverd.... you already hit a home run man! And it didn't involve any magical dematerialization of supporting structure, nor did it require any machinations like those that have, of necessity, blossomed from the aerostatic model as it's evolved, attempting to explain something it can't possibly explain. The (when applied to the building) inherently miraculous aerostatic example of the "brick shed aerostatic blowout" absolutely fails to display even a tenuous behavioural correspondence with observations. Of the two examples you originally mentioned (gas explosion and aerostatic bursting), it's actually the extraordinarily simple gas explosion example of the brick shed you mentioned that superiorly displays an immediate and solid one to one behavioural correspondence with observations and accounts for the emergence at some point of the conditions required for free fall to arise. No miracle there.... good job!

When comparing the aerostatic model to the gas explosion model, unlike the Rube Goldberg aerostatic model, the gas explosion model easily replaces all of the above with a single sentence....

Judging by the confirmed observation of a significant period of gravitational acceleration, a high probabilty exists that a gas or other type of explosion or event must have occurred that was powerful enough to quickly remove the support from beneath the upper part of the building, either all at once or incrementally in advance of its descent (right), permitting it to descend at gravitational acceleration for the observed period of time and under the conditions required (left) for free fall to occur....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F8db27a83092f9cb1be47bba39ea92628.gif&hash=70fde890e8f9091743cb39d2faa91d2d)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2Fd09871fcde64ba30384a87220d9837b4.gif&hash=e6217b75adbea43f86f6c9eeb813f68f)

I think I'm done with the aerostatic model, but there is one thing I'm really curious about though. When you originally considered/came up with those two examples.... How did you manage the Olympically executed Herculean pole vault over Occams razor?

Can you try to delineate for me in a simple step-by-step way what the line of reasoning was that led you to choose the aerosatic model over the gas explosion model as being most probable (if you recall)?
 
Title: Re: What is free fall?
Post by: alancalverd on 31/12/2013 20:23:37
No.

You said the fire was some way down the building (8th floor?) so the movement of the west penthouse clearly isn't the first stage of collapse - it just happens to be the first externally visible sign. We have no idea of the state of the intermediate floors.

Had there been a gas explosion you would expect to see (a) the shockwave emanating from the level of the explosion, not from  near the top of the building (b) significant ejecta from that level and (c) not a lot of collapse since the steel frame would probably have withstood a contained burst at one level - more likely to have blown out the windows symmetrically without damaging the steelwork or breaching the floors.

Intentional explosive demolition is done by attaching simultaneous high-explosive charges (gas is not a high explosive) to the steelwork itself, to produce the kind of torsional failure that I think probably occured here. 

And remember that aerostatic blowout isn't the whole picture - it merely renders the structure "unstiff" and therefore unable to support torsional loads as the floors collapse.

I like the idea of polevaulting over Occam's razor. But given the starting conditions you offered, with no suggestion or evidence of a gas explosion, much less of a continuing fire during the descent, I wouldn't have used gas as the pole.

Quote
a process that "progressively disintegrated" the support structure below (spontaneous catastrophic progressive structural disintegration.... a novel mode of structural failure?).

That's what you can see on the video - at least the external evidence. Our task is to explain it.
Title: Re: What is free fall?
Post by: Aemilius on 31/12/2013 21:03:58
Thank you for that in depth analysis of why a gas explosion wouldn't bring down the building, but I didn't limit the cause of the explosion to gas alone, what I said was....


"....a high probabilty exists that a gas or other type of explosion or event must have occurred that was powerful enough to quickly remove the support from beneath the upper part of the building, either all at once or incrementally in advance of its descent...."
Title: Re: What is free fall?
Post by: alancalverd on 01/01/2014 11:38:19
As we discussed earlier, if you remove the support explosively, the upper stories will accelerate immediately at a rate close to g. They didn't.
Title: Re: What is free fall?
Post by: Aemilius on 04/01/2014 18:15:22
Intentional explosive demolition is done by attaching simultaneous high-explosive charges (gas is not a high explosive) to the steelwork itself, to produce the kind of torsional failure that I think probably occured here.

No. Intentional explosive demolition is rarely done by attaching simultaneous high-explosive charges to the steelwork.... it's done by attaching precision timed high-explosive charges to the steelwork.
 
Quote
a process that "progressively disintegrated" the support structure below (spontaneous catastrophic progressive structural disintegration.... a novel mode of structural failure?).

That's what you can see on the video - at least the external evidence. Our task is to explain it.

Misplaced concreteness, Mr. Calverd?

As we discussed earlier, if you remove the support explosively, the upper stories will accelerate immediately at a rate close to g. They didn't.

And as I just pointed out, simultaneous detonation of the charges is rare. In fact, since the detonations can be (and routinely are) precisely timed, the door is thrown wide open for a variety of possible outcomes. One could quickly detonate all the charges at once for immediate acceleration to free fall, or one could detonate them slowly over time, including a period of free fall at any point one wished.... so that's not ruled out yet. 

To sum up....

My position is that not only is it impossible for the lower part of the building to have progressively/naturally collapsed in any way that could have resulted in the upper part of the building descending at anything near gravitational acceleration (below left) for any period of time during it's descent (below right), but also that there is absolutely no mode or combination of modes of progressive/natural structural failure driven solely by gravity that could ever give rise to the conditions required for anything near free fall to occur at any point during its descent....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fa0cb7908dee38177e36e60b0cc7d95f6.gif&hash=6f33a99ca916bcba11db979a8f8cf484)

Your position (unless I'm misunderstanding things incorrectly) is that not only is it somehow possible for the lower part of the building to have progressively/naturally collapsed in a way that would result in the upper part of the building accelerating as it descended (below right), but also that, driven solely by gravity, it would actually continue to accelerate so nearly to gravitational acceleration (below left) as to require careful calculation for any difference between the two to be detected....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi.picasion.com%2Fpic76%2F5b9c4cc103d2e6272956c87cf5443cf1.gif&hash=f76874ddf193428baffc24e0ea94fc5b)

I don't see how it can to do us any good to continue researching all the possible structural failure modes (or even make up new ones) in the hope of finding that special one that can create the conditions required for even near-free-fall to occur because it's physically impossible.

When it comes to your "catastrophic aerostatic blowout"....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fe7c961fb4327cc8a1b3beb310a7fa003.gif&hash=60412c4c06a5a92396f4f91847a6e9e6)

...."speed of sound stress propagation shockwaves"....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fb2ba79541e97f5393f4e7ec84b68920d.gif&hash=daf37bef3d28b9c70bd104bbbf60825f)

...."spontaneous progressive structural disintegration" theory....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F6feff1cd4625a93e2cd98e4a97cda712.gif&hash=ffd93b719d5954529ca0da3211f31c02)

We'll just have to shake hands, agree to disagree.... and return to our respective universes.

P.S. - Diogenes, your posthumous guest and loyal eulogist, told me to tell you that.... "Though Perpetual Motion may be impossible, take heart, for the 'Oxford Bell' continues to ring!"
Title: Re: What is free fall?
Post by: alancalverd on 04/01/2014 23:50:41
'
Quote
I don't see how it can to do us any good to continue researching all the possible structural failure modes (or even make up new ones) in the hope of finding that special one that can create the conditions required for even near-free-fall to occur because it's physically impossible.

Suit yourself, but on my planet we assume that what we see and measure is indeed physically possible.

Never believe a philosopher - especially one that lives in a barrel. Trust your own eyes.
Title: Re: What is free fall?
Post by: Aemilius on 05/01/2014 11:38:39
....on my planet we assume that what we see and measure is indeed physically possible.

Apparently you can see and measure things that aren't even there.... Must be some planet!

At almost the exact same time as the West Penthouse begins to break up and descend, there's evidence of venting five or so stories below it and out the top of the building above it as well.... but you see a massive multi-floor piston instantly causing a catastophic aerostatic blowout and powerful shockwave (all created by just the first few feet of the descent of the West Penthouse).
 
There's really nothing but a puff of smoke/dust at the first purported blowout.... but you see evidence of not just one but multiple aerostatic blowouts and shockwaves having occurred.

At almost the exact same time as the West Penthouse begins to descend, windows begin to shatter down and across the facade over multiple floors with no accompanying ejecta whatsoever, no smoke, no papers, no dust, nothing. Only a structural flexure can explain that (there was no pressure behind the windows).... but you see a powerful aerostatic shockwave racing accross the building through both walls and floors (all created by just the first few feet of the descent of the West Penthouse).

Though not one panel of cladding is seen to be dislodged during any of this.... you see evidence of multiple aerostatic blowouts having dislodged enough cladding/windows around the building to seriously affect its rigidity.

Though the entire facade of the building remains largely intact as it descends and there's no visible sign of any buckling or structural failure having been caused by the roof moving.... you actually see a mysterious new failure mode that can cause spontaneous widespread catastrophic progressive disintegration of steel columns.
 
Is there even one recorded incident of anything like this ever actually happenning that would tend to support your assertion about how the building came down?
Title: Re: What is free fall?
Post by: Aemilius on 05/01/2014 13:28:50
Interesting to note that I'm not getting slapped around (as I'm accustomed to), but neither is there any chorus of support for your explanation either Mr. Calverd. Even if one subtracts my 1,749 edits, there're still quite a few "views of the thread.... Where do the rest of you fall on this issue?
Title: Re: What is free fall?
Post by: Bored chemist on 05/01/2014 14:10:04
I can't speak for anyone else, but I didn't bother to get involved in this discussion because I got bored of refuting absurd claims about the tower falling years ago.

All the evidence supports Alan's point of view.

It fell down because some shits flew a plane full of jet fuel into it.
That fire heated the steelwork until it failed. The upper floors fell down and, since skyscrapers are not designed to take massive vertical shock loads, the rest collapsed.
It's not possible to analyse the video footage accurately enough to measure the acceleration to a high enough precision to rule out near free fall.
Typical video pictures are about 500 hundred lines high, and the image falls through about half the frame height so, at best you can measure the height of the building in each frame to about 1 part in 250.
That's simply not enough precision to rule out the suggestion that the building fell down.

You have, essentially, no evidence; but you have wasted 5 pages talking about it.

Anyone joining in with the discussion to point this out to you wouldn't have stopped you rambling on about it.
Title: Re: What is free fall?
Post by: Aemilius on 05/01/2014 15:07:43
I can't speak for anyone else, but I didn't bother to get involved in this discussion because I got bored of refuting absurd claims about the tower falling years ago.

Well, like I said, I'm a relative newcomer to the internet so, sorry if it's already been exhaustively discussed. As far as absurd claims go, I haven't made any claims. So far we've just discussed Mr. Calverd's absurd claims.

All the evidence supports Alan's point of view.

And precisely what "evidence" is that Bored chemist?

It fell down because some shits flew a plane full of jet fuel into it.[

Indicating that you haven't a clue as to what Mr. Calverd and I have been discussing for the last 100 or more posts!

That fire heated the steelwork until it failed. The upper floors fell down and, since skyscrapers are not designed to take massive vertical shock loads, the rest collapsed.

Conclusively proving that you haven't a clue as to what Mr. Calverd and I have been discussing for the last 100 or more posts!

It's not possible to analyse the video footage accurately enough to measure the acceleration to a high enough precision to rule out near free fall.

Hah! Yeah, sure pal, everyone knows your assessment trumps the NIST.... Ridiculous! High enough precision to rule out near free fall?  What does that even mean?
 
Typical video pictures are about 500 hundred lines high, and the image falls through about half the frame height so, at best you can measure the height of the building in each frame to about 1 part in 250.

I'll get you the email address for the NIST. Why bother me with it? Take it up with them!

That's simply not enough precision to rule out the suggestion that the building fell down.

Not precise enough to rule out the suggestion that the building fell down? Hilarious! You're a riot man.... you're going to be bigger than Jerry Seinfeld! 

You have, essentially, no evidence; but you have wasted 5 pages talking about it.

I don't know about the five wasted pages bit, but somehow you've managed to squeeze a whole truckload of waste into just one post. Very impressive!  And when the hell did I ever say I had any "evidence" of anything? Got a quote.... Or would you like to just keep making it up as you go along?

Anyone joining in with the discussion to point this out to you wouldn't have stopped you rambling on about it.

Well, Bored chemist, I can say with confidence that your joining the discussion certainly didn't change a thing! Ask yourself this Einstein....

Why would a bunch of jibberish coming from someone who doesn't even know what the topic is change anything? Your whole post is a bunch of worthless crap!

If you're supposed to be the chorus of support for Mr. Calverd.... woe to Mr. Calverd.

Title: Re: What is free fall?
Post by: alancalverd on 05/01/2014 15:29:52
Quote
Though the entire facade of the building remains largely intact

A couple of inches is all it takes.

Anyway, enough of my hypotheses. What do you think happened?
Title: Re: What is free fall?
Post by: Aemilius on 05/01/2014 15:34:05
Right, now it's a couple of inches, before it was a couple of feet.... C'mon!

What do I think happened? I'm nobody.... Who cares what I think? You're the Physicist, you're the one who's supposed to deliver scientific truth to me, not the other way around. I don't feel you're doing that (nothing personal).
Title: Re: What is free fall?
Post by: alancalverd on 05/01/2014 15:48:11
If we are being pernickety, it's Dr Calverd, if you don't mind.
Title: Re: What is free fall?
Post by: Aemilius on 05/01/2014 15:49:58
You mean persnickety? Well we're not so it will remain Mr. Calverd, unless you really find it objectionable.... Would you prefer "Dr. Calverd" Mr. Calverd? From now on I'll refer to you as "Dr. Allen Caverd Ph.D. Physicist"
Title: Re: What is free fall?
Post by: Aemilius on 05/01/2014 17:05:46
Now that we've addressed all the etiquette issues Dr. Allen Calverd Ph.D. Physicist.... Was there any forthcoming response to reply 111?
Title: Re: What is free fall?
Post by: alancalverd on 05/01/2014 17:12:09
Alan
Title: Re: What is free fall?
Post by: Aemilius on 05/01/2014 17:18:42
Right (terribly sorry), "Dr. Alan Calverd Ph.D Physicist".... got it. Was there an actual response to reply 111?
Title: Re: What is free fall?
Post by: alancalverd on 05/01/2014 17:26:29
#115, IIRC
Title: Re: What is free fall?
Post by: Aemilius on 05/01/2014 17:53:46
So all of reply 111....

Apparently you can see and measure things that aren't even there.... Must be some planet!

At almost the exact same time as the West Penthouse begins to break up and descend, there's evidence of venting five or so stories below it and out the top of the building above it as well.... but you see a massive multi-floor piston instantly causing a catastophic aerostatic blowout and powerful shockwave (all created by just the first few feet of the descent of the West Penthouse).
 
There's really nothing but a puff of smoke/dust at the first purported blowout.... but you see evidence of not just one but multiple aerostatic blowouts and shockwaves having occurred.

At almost the exact same time as the West Penthouse begins to descend, windows begin to shatter down and across the facade over multiple floors with no accompanying ejecta whatsoever, no smoke, no papers, no dust, nothing. Only a structural flexure can explain that (there was no pressure behind the windows).... but you see a powerful aerostatic shockwave racing accross the building through both walls and floors (all created by just the first few feet of the descent of the West Penthouse).

Though not one panel of cladding is seen to be dislodged during any of this.... you see evidence of multiple aerostatic blowouts having dislodged enough cladding/windows around the building to seriously affect its rigidity.

Though the entire facade of the building remains largely intact as it descends and there's no visible sign of any buckling or structural failure having been caused by the roof moving.... you actually see a mysterious new failure mode that can cause spontaneous widespread catastrophic progressive disintegration of steel columns.
 
Is there even one recorded incident of anything like this ever actually happenning that would tend to support your assertion about how the building came down?

....is explained by reply 115....

A couple of inches is all it takes.

Oh man.... that's rich!
Title: Re: What is free fall?
Post by: Aemilius on 06/01/2014 01:07:05
I think it's been an interesting and informative conversation. I see your theory Dr. Calverd, and even though I believe I've shown it to be completely baseless and thoroughly disagree with it, it's your theory and you're welcome to it. I think I'll leave it at that and just read the opinions/theories of others (if any) and respond to those, as we've reached something of an impasse.

Thanks again sincerely for all your responses Dr. Calverd, looking forward to corresponding with you again.... maybe next time something a little less controversial. Thanks to everyone else that commented too (except you Bored chemist!). 
Title: Re: What is free fall?
Post by: Aemilius on 06/01/2014 17:47:47
....I got bored of refuting absurd claims about the tower falling years ago.

If your entrance is any example, you couldn't refute a fairy tale.

Title: Re: What is free fall?
Post by: Aemilius on 09/01/2014 02:34:11
This was presented as an anonymous 47 story tall building so there wouldn't be any reason for any theory to fall into the category of "Not Allowed" or "Off Limits". All a theory has to do is be consistent with physical principles and display a solid behavioural correspondence (a predictable outcome similar to confirmed observations) in order not to be "ruled out" as a possible contender that explains the whole thing. It's not a whodunit, it's a howdidit. For the analysis it doesn't matter who the tenants may have been, why anyone might have done it, how they could have done it, whether anyone saw Bin Laden's face in the smoke or a lizard changing into George W. Bush, or even what the name of the building was or where it was located.... and it doesn't matter if "some shits" were flying around in planes full of jet fuel either.

My position hasn't changed....

It's physically impossible for the lower part of the building to have progressively/naturally collapsed (below) in any way that could result in the upper part of the building symmetrically descending straight down through itself, through the path of greatest resistance at anything near gravitational acceleration for any period of time, and there is absolutely no mode or combination of modes of progressive/natural structural failure driven solely by gravity....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fd50f4f801b0c3dfb6c3a5b908d4b6faa.gif&hash=caf45b067bffdf26321f9c3e3b2dfbe7)

....that can ever give rise to the conditions required (below) for free fall to have occurred at any point during its descent....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F8db27a83092f9cb1be47bba39ea92628.gif&hash=70fde890e8f9091743cb39d2faa91d2d)

....and anyone who believes otherwise (below) belongs in a lunatic asylum.....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F9fda7447ab53a056ff5f02c28634ecb3.gif&hash=d6fd60056393308da5bd58bb43bf64f0)

 
So, Bored chemist, if you want to haul yourself aboard the sinking ship of Dr. Calverds theory and believe all the evidence supports his point of view, at what point during his theoretical post catastrophic aerostatic blowout/speed of sound stress propagation/spontaneous progressive structural disintegration collapse would you say....
 
"Hold it.... Right there! That's the point where all the columns
will undoubtedly be found behaving in a manner very
much like air (left).... it will take very careful calculation
to tell the fall times apart during this period of
the ongoing progressive structural failure (right)."

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fa0cb7908dee38177e36e60b0cc7d95f6.gif&hash=6f33a99ca916bcba11db979a8f8cf484)

Dr. Calverds position is that not only is it possible but probable that the lower part of the building progressively/naturally collapsed in a way that resulted in the upper part of the building actually accelerating as it descended symmetrically straight down through itself, through the path of greatest resistance (below right), and also, incredibly, that driven on solely by gravity it actually continued to accelerate so nearly to gravitational acceleration (below left) as to require very careful calculation for any difference between the two to be detected.

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi.picasion.com%2Fpic76%2F5b9c4cc103d2e6272956c87cf5443cf1.gif&hash=f76874ddf193428baffc24e0ea94fc5b)

I don't really have a theory per se, but if I had to choose one, it would obviously have to be Dr. Calverds other model, the "explosion" model (below left) that was skipped over in favor of the "aerostatic" model (below right) because the explosion model, unlike the aerostatic model, can actually create the conditions required for free fall to occur (below center). The explosion model clearly shows an immediate and solid one to one behavioural correspondence with the confirmed observation of gravitational acceleration, and it can easily account for that at any point during the descent of the upper part of the building anytime one wishes.... in contrast to the fantastic catastrophic aerostatic blowout/speed of sound stress propagation/catastrophic spontaneous progressive disintegration invention that, oh yeah, leaves all the columns and support structure in place!

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Ff24d4093dd7e5ed00a0fdba686ee42a3.gif&hash=e80805776247ac4ef83ef741b49df33d)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fcbd066d27eeaed9412d495b324a0a186.gif&hash=4c84ab5e173e8a3918e4aafa4eb163b8)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F115c6d9b36148d757137463278611934.gif&hash=32bbb1986275f07e77064f9c1a5d4a31)

So far, the explosion model (below) is the only one....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2Fd09871fcde64ba30384a87220d9837b4.gif&hash=e6217b75adbea43f86f6c9eeb813f68f)

....that can realistically match and be expected to create the conditions (below) that we know must have existed....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F8db27a83092f9cb1be47bba39ea92628.gif&hash=70fde890e8f9091743cb39d2faa91d2d)

....beneath the literally falling visible upper part of the building (below) during its observed largely symmetrical descent at gravitational acceleration for approximately 105 feet in 2.25 seconds.

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F0d8f489c42d14f50777e0d8e90059b6a.gif&hash=ec7e55896d81c088b4e19d42f480a2bb)

So the closest thing to a theory I have (and in answer to Dr. Calverds earlier question about what I think happenned), at least at this point, would go something like....

Judging by the confirmed observation of a significant period of gravitational acceleration, a high probabilty exists that an explosion or other type of event must have occurred that was powerful enough to quickly remove the support from beneath the upper part of the building (below right), either all at once or incrementally in advance of its descent, permitting it to descend at gravitational acceleration for the observed period and under the conditions required (below left) for free fall to occur.

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fef4a740c36efe88f565475ebbbbf3887.gif&hash=b3f9c7a110be86d92712c2b8561301eb)


Title: Re: What is free fall?
Post by: Bored chemist on 12/01/2014 13:13:31
....I got bored of refuting absurd claims about the tower falling years ago.

Care to show what's wrong with my assertion about the number of video lines, and the best available precision on the fall rate?
Title: Re: What is free fall?
Post by: alancalverd on 13/01/2014 11:50:59
OK, back in the swim.

Let's have an explosion. But it clearly (according to the NIST velocity graph) occured about 2 seconds after the west penthouse started moving so it wasn't the primary cause of collapse, nor did it cause much debris to be ejected. A very interesting scenario indeed. How was it orchestrated, and what explosive produces more suck than blow?
Title: Re: What is free fall?
Post by: Aemilius on 13/01/2014 22:32:19
OK, back in the swim.

Thank God (figuratively speaking).
Title: Re: What is free fall?
Post by: JP on 16/01/2014 23:26:29
Calling other people's claims "worthless crap" is pushing the rule to "keep it friendly" on the forum.  Please try to stay civil in here.

Thanks,
The Mods
Title: Re: What is free fall?
Post by: Aemilius on 21/01/2014 21:11:04
Hello JP (nice to meet you)....

I understand the "keep it friendly" rule JP, and I think the fact that the ongoing discussion between Dr. Calverd and I has been a perfectly civil and enjoyable exchange (even when mildly contentious) clearly demonstrates that. I'll not repeat what I said earlier, but neither will I take it back. When it comes to the insulting monument to irrelevance that is reply 113 though, let me ask you this....

How does one respond to an immediate and open display of hostility in a "friendly and civil" way? Between just which two blows of his broadsword did you expect me to reach out to this Bored chemist fellow?
Title: Re: What is free fall?
Post by: Aemilius on 21/01/2014 21:14:35
Hi Dr.Calverd....
 
Especially interested (actually dying) to read your take on all this.... Can you make sense of anything this Bored chemist fellow has written?
 
By the way, I'm looking forward to exploring the explosion model with you, but since we're sort of in between the "aerostatic" and "explosion" models, I think I'll take a bit of a break for a week or so. Just wanted you to know I haven't lost interest.

Take care.
Title: Re: What is free fall?
Post by: Aemilius on 21/01/2014 21:16:12
Hey Bored chemist....

Look man, in spite of the Moderators admonition, I have to stand by my characterization of your reply 113....

I can't speak for anyone else, but I didn't bother to get involved in this discussion because I got bored of refuting absurd claims about the tower falling years ago.

All the evidence supports Alan's point of view.

It fell down because some shits flew a plane full of jet fuel into it.
That fire heated the steelwork until it failed. The upper floors fell down and, since skyscrapers are not designed to take massive vertical shock loads, the rest collapsed.
It's not possible to analyse the video footage accurately enough to measure the acceleration to a high enough precision to rule out near free fall.
Typical video pictures are about 500 hundred lines high, and the image falls through about half the frame height so, at best you can measure the height of the building in each frame to about 1 part in 250.
That's simply not enough precision to rule out the suggestion that the building fell down.

You have, essentially, no evidence; but you have wasted 5 pages talking about it.

Anyone joining in with the discussion to point this out to you wouldn't have stopped you rambling on about it.

I openly challenged you to back it up (using quotes/links/articles) or take it back and you've done neither. Instead, you now seem more interested in trying to take the helm and steer the focus of the thread to grilling me about why some aspect of your invisible plane full of jet fuel claim/assertion won't work, and now you're even trying to imply an appeal to authority on my part for citing NIST data, ostensibly in support of some imaginary claim you think I've made....  I've advanced no theory, nor have I made any claims or assertions of any kind.
 
Why are you demanding answers to questions from the anonymous eighth grade dropout questioner instead of just asking Dr. Calverd, a recognized bona fide veteran research Physicist eminently qualified to answer them? As anyone can see, you're just not making any sense!

I don't have any academic credibility and I didn't come here to give answers, I came here to get answers from the brighter lights here. I didn't set out to see you in a negative light either, but until you address/account for what you wrote in reply 113, I have no choice....

At this point you've proven nothing, you've backed up nothing, you've taken back nothing, you've refuted nothing, your invisble fuel laden plane theory (if that's what it is) makes no sense and your focus on me instead of the topic is just odd.... I honestly can't see where you've really said anything at all!

In view of all that and pending some sort of coherent explanation, I'm just going to ignore your posts.
Title: Re: What is free fall?
Post by: JP on 21/01/2014 22:41:36
How does one respond to an immediate and open display of hostility in a "friendly" way? Between just which two blows of his broadsword did you expect me to reach out to this Bored chemist fellow?

You're supposed to keep the tone of the conversation friendly and civil.  If you (or other users) can't do this, the thread will be locked.  Your recent responses are in line with this rule of civility.
Title: Re: What is free fall?
Post by: MrVat7 on 22/01/2014 08:15:27
Falling under action of only one force - gravity
Title: Re: What is free fall?
Post by: Bored chemist on 22/01/2014 19:20:25
Hey Bored chemist....

Look man, in spite of the Moderators admonition, I have to stand by my characterization of your reply 113....

I can't speak for anyone else, but I didn't bother to get involved in this discussion because I got bored of refuting absurd claims about the tower falling years ago.

All the evidence supports Alan's point of view.

It fell down because some shits flew a plane full of jet fuel into it.
That fire heated the steelwork until it failed. The upper floors fell down and, since skyscrapers are not designed to take massive vertical shock loads, the rest collapsed.
It's not possible to analyse the video footage accurately enough to measure the acceleration to a high enough precision to rule out near free fall.
Typical video pictures are about 500 hundred lines high, and the image falls through about half the frame height so, at best you can measure the height of the building in each frame to about 1 part in 250.
That's simply not enough precision to rule out the suggestion that the building fell down.

You have, essentially, no evidence; but you have wasted 5 pages talking about it.

Anyone joining in with the discussion to point this out to you wouldn't have stopped you rambling on about it.

I openly challenged you to back it up (using quotes/links/articles) or take it back and you've done neither. Instead, you now seem more interested in trying to take the helm and steer the focus of the thread to grilling me about why some aspect of your invisible plane full of jet fuel claim/assertion won't work, and now you're even trying to imply an appeal to authority on my part for citing NIST data, ostensibly in support of some imaginary claim you think I've made....  I've advanced no theory, nor have I made any claims or assertions of any kind.
 
Why are you demanding answers to questions from the anonymous eighth grade dropout questioner instead of just asking Dr. Calverd, a recognized bona fide veteran research Physicist eminently qualified to answer them? As anyone can see, you're just not making any sense!

I don't have any academic credibility and I didn't come here to give answers, I came here to get answers from the brighter lights here. I didn't set out to see you in a negative light either, but until you address/account for what you wrote in reply 113, I have no choice....

At this point you've proven nothing, you've backed up nothing, you've taken back nothing, you've refuted nothing, your invisble fuel laden plane theory (if that's what it is) makes no sense and your focus on me instead of the topic is just odd.... I honestly can't see where you've really said anything at all!

In view of all that and pending some sort of coherent explanation, I'm just going to ignore your posts.

Care to show what's wrong with my assertion about the number of video lines, and the best available precision on the fall rate?
Title: Re: What is free fall, and its relation to implosions and building collapse?
Post by: Aemilius on 26/01/2014 22:41:09
Well Bored chemist, your last post makes just as much sense as your first.... none. At least you're consistent!

It's been about three weeks now since you crash landed in this thread with the monument to irrelevance that is reply 113. All you've done since then is to repeat the same question like an old broken record player. Do you think it makes you appear intelligent endlessly waving around the same question about the precise measurement of free fall Bored chemist? Do you think that maybe it distracts people from noticing that your posts lack even a nanogram of substance/relevance? How long will you continue with this buffoonery? Everyone can see there's no logical explanation for it.... What's the deal man?

As it turns out, you're the one who's actually doing all the things you've accused me of. It is you who has made an absurd and easily refuted claim. It is you who has no evidence, essential or otherwise, supporting your view. It is you who continues to "waste space". It is you who continues to ramble on, repeating the same question in response to my repeated requests that you back up what you wrote.

Care to show what's wrong with my assertion about the number of video lines, and the best available precision on the fall rate?

I already told you, I'm just an eighth grade dropout, so I can't honestly say I know what's wrong with your so called "assertion" about the number of video lines or what the best available precision is on the fall rate. I tried to ask Dr. Calverd for his opinion of it in reply 135. My guess is the reason he hasn't responded is that he sees your post as radioactive and doesn't want to get anywhere near it. Why don't you try asking him yourself? Why are you avoiding that option here?

You may think you're being clever with all this nonsense, but the only one you're fooling is yourself. Go ahead and keep responding though if you enjoy watching what's left of your now shredded credibility in this thread repeatedly being raked over the coals (in a friendly and civil way of course) by an eighth grade dropout!
Title: Re: What is free fall, and its relation to implosions and building collapse?
Post by: alancalverd on 28/01/2014 00:44:32

Care to show what's wrong with my assertion about the number of video lines, and the best available precision on the fall rate?

Behave, children!

If the reference point just crosses 200 lines, and there's no uncertainty in the timebase, you can estimate the fall distance to better than +/- 0.5% and the elapsed time to within a couple of microseconds by simple frame analysis. Modern videocamera timebases are very stable and consistent. The NIST graph seems pretty good to me.
Title: Re: What is free fall, and its relation to implosions and building collapse?
Post by: Aemilius on 28/01/2014 06:40:40
Excellent Dr. Calverd, and just what I intuitively suspected (but might have had a bit of trouble elucidating).

Just to be clear though.... You're saying the assertion being made by Bored chemist that it's not possible to analyse the video accurately enough to prove free fall/near free fall is in error.

Is that correct?
Title: Re: What is free fall, and its relation to implosions and building collapse?
Post by: alancalverd on 28/01/2014 08:15:19
I think NIST can analyse a video reasonably well.
Title: Re: What is free fall, and its relation to implosions and building collapse?
Post by: Aemilius on 28/01/2014 08:21:26
I'll take that as a "Yes".
Title: Re: What is free fall, and its relation to implosions and building collapse?
Post by: Aemilius on 29/01/2014 07:59:43
I think I'll skip any further discussion of this, it's actually starting to give me the creeps....

I have Dr. Alan Calverd Ph.D. (a well seasoned career research physicist) arguing that not only is it possible but probable that the lower part of the building progressively/naturally collapsed in a way that resulted in the upper part of the building actually accelerating as it descended symmetrically straight down through itself, through the path of greatest resistance (below left), and also, incredibly, that driven on solely by gravity it quite naturally continued to accelerate so nearly to gravitational acceleration (below right) as to require very careful calculation for any difference between the two fall times to be detected.... preposterous!

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F9fda7447ab53a056ff5f02c28634ecb3.gif&hash=d6fd60056393308da5bd58bb43bf64f0)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F8db27a83092f9cb1be47bba39ea92628.gif&hash=70fde890e8f9091743cb39d2faa91d2d)

There appears to be a considerable number of views of the thread but, eerily, not one member is commenting on the veracity of what I've had to say, and neither is anyone commenting on the veracity of what Dr. Calverd has had to say either.... very strange indeed!
 
A clearly irrational and insulting post made by Bored chemist slips past the moderators, but I am openly admonished for not "keeping it friendly" when I bluntly challenge/recognize his absurd baseless assertion for what it is.... a now confirmed load of rubbish!

Finally, CliffordK has explained to me (privately) that he and the other moderators decided that arguments about whether or not two jet airplanes caused the building to collapse seemed best suited to the "That CAN'T be true" subforum, though no airplane struck the building (even the NIST says airplanes had nothing to do with it) and airplanes are mentioned nowhere in the thread as having had anything to do with it either.... extremely curious!

To top it all off, compared to the meticulously factual and clearly defined hard science question I posed concerning the obvious impossibility of even near free fall occurring during any natural progressive structural failure, there seems to be no problem with topics like how much to tax the price of a drink or baggy shirts causing some guy to sweat being considered as "General Science"..... incredible!

Not meant to offend, I just don't get any of that. Thread abandoned (for now).... Lock it, leave it, do as you wish.

Title: Re: What is free fall?
Post by: Aemilius on 12/09/2014 07:43:17
Quote from: alancalverd
Let's have an explosion.

Right Dr. Calverd, we might as well, since, as we've both really
known all along, it's the only logical way to explain observations.

WTC7 - ANALYSIS AND CONCLUSION

A complete Prima Facie Empirically Verifiable Scientific
Method Driven Graphical Target System Analysis and
Conclusion arrived at by Process of Elimination


(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fs4.postimg.org%2F6zmv19f3x%2FCapturetower.jpg&hash=2208bea7782e8d143f5355beab637946)

"Analogical models are a method of representing
a phenomenon of the world, often called the 'target system',
by another, more understandable or analysable system. They
are also called dynamical analogies." - Wikipedia


The exceptionless condition required for gravitational acceleration
to occur has been known for centuries....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F9383be58c2196650abf48981db503779.gif&hash=73a7cfc0ffae5045ec13d95829a9fa4d)

....and is, as you pointed out initially "The condition under which
a body is, literally, free to fall under the influence of the local
gravitational field with no resistance to its acceleration.
"....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F78fe757793d30a322732edd16cff4bde.gif&hash=3b38c60fdf117bb618d90bba83f4e460)

The Control, or source system, that appears to the right of the
Scenario, or target system, in many of the animations is
intended as a reminder of that, and also signals the
beginning of a comparison....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi.picasion.com%2Fpic76%2Fef2992a1bed34a1ad9d2e8f520c5ad7e.gif&hash=5f57376c82f20c3a60a1033239464695)

We can still know with certainty what condition exists beneath
an object as it falls....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F255b5e6b0f1f20b0bd95d84a94ef1386.gif&hash=120ac30ce371850b42bb6c74fd8318bc)

....even though we may not be able to see into the space
beneath it as it does....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F1036ed956866bb76e5e518d9c4e7a69c.gif&hash=ab9cc405b00f82c449c66b34fcc956cf)

Buckled columns, whether one or a hundred, whether one at a
time or all at once (or any combination thereof) won't just go
from 100% to 0% when they buckle, they'll gradually
decrease in strength while they buckle
and that takes time....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2Ff2176b9174d6af03e8c18ccb0ac38867.gif&hash=21ef95bd467d5e2ac03b2f5df212d189)

The mechanism of buckling (a mode of natural progressive
structural failure), whether caused by heat....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F171da9bd639a474f93f75416474f53ce.gif&hash=85cbc019fdd604418c2f91dfb5ef006e)

....or by overloading....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fa338ba3cef6cdac0cc13fe19a7c5c2bc.gif&hash=74af5a6ed9dfd9e898acf549f989cd15)

....or by other modes of natural progressive structural failure
such as impact induced fracturing....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F189367ead1f1173ae0821bc21a4cb949.gif&hash=23a76c51de204084df65fcf9bc6431a7)

....or fracturing caused by overloading....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F491b34f1ef51fec27a6311f7b36e362d.gif&hash=fc92fdfc6b1d70bafe0fe54ec5e8fa28)

....or any other mode or combination of modes of natural
progressive structural failure absolutely cannot match or
create the exceptionless condition required for gravitational
acceleration to occur, it's literally impossible (naturally excluding
the consideration of bridges and other structures that pass through
air wherein the condition required for gravitational acceleration to
occur exists inherently as a structural feature). There is no such
thing as structural gravitational acceleration....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fd5dbd5d68ab7326804067a722fe8bc06.gif&hash=7e70d6df2ef33d054d6de5f31e816578)

The progressive collapse of the building (NIST probable
collapse sequence starting with column 79 on the left)....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F06c559cd5c8a1df0aa4d57e1ed06ff51.gif&hash=6240b1956053c5906a144e94d36d2f9e)

....that essentially happens all at once....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F9c68e547d22a337a9448b8c21d55fe12.gif&hash=659787a1a046bcc5f442d8431ed9efd8)

....is clearly physically inconsistent with what we
empirically know of natural progressive structural failure
(defined as a time consuming process of individual, sequential
or simultaneous failure involving one or a number of related
structural components). It's a physical impossibility for the
lower part of the asymmetrically damaged building
(reportedly three core columns and nine perimeter
columns) to have naturally progressively collapsed
in any way that could result in the upper part of
the building symmetrically descending as a single
unit straight down through itself.... 

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2F911research.wtc7.net%2Fmirrors%2Fguardian2%2Fvideo%2Fwtc7.gif&hash=993ceb5da8d5a5d3212c448765977da2)

....at anything near gravitational acceleration (NIST
probable collapse sequence starting with column 79 circled
below) for any period of time....

(https://web.archive.org/web/20151125150917im_/http://picasion.com/pic76/27116a12288329cea1fc0a4cf817d33a.gif)

A building collapse like that seen below resulting from any
natural progressive structural failure of a steel frame building
including a 105 foot 2.25 second period of gravitational
acceleration of the upper part of the building as a single
unit is an absolute physical impossibility....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fs9.postimg.org%2Fgu7urbxin%2Fwtc7channel9ve7_gif_wtc.gif&hash=cf8df568f9a734adea573ddd503ffa93)

....as nowhere in the course of any such collapse or
structural failure is the exceptionless condition required
for gravitational acceleration to occur seen to arise beneath
the upper part of the building as the scenario
plays out to completion....

(https://web.archive.org/web/20151125150917im_/http://s14.postimg.org/dl7ec06xr/oie_animation.gif)

There is absolutely no mode or combination of modes
of natural progressive structural failure driven solely
by gravity that can ever match or give rise to the
exceptionless condition required for free fall to have
occurred at any point during it's descent....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F8db27a83092f9cb1be47bba39ea92628.gif&hash=70fde890e8f9091743cb39d2faa91d2d)

The scenario playing out below is an absolute physical
impossibility. Just as there is no such thing as structural
gravitational acceleration
, nor is there any structural failure
mode known as natural progressive structural
gravitational acceleration
....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F9fda7447ab53a056ff5f02c28634ecb3.gif&hash=d6fd60056393308da5bd58bb43bf64f0)

There is simply no point during a natural progressive gravity
driven collapse of any modern steel frame skyscraper
where one could realistically say....

"Hold it.... right there! That's the point past which all
the welded and bolted together steel columns and
structural components
that were supporting the building
just a moment ago (with an area greater than that of
a football field) will undoubtedly be observed beginning
and then continuing to behave in a manner indistinguishable
from  air
(below left) for at least the next eight stories,
or 105 feet
of its descent (below right). It would take very
careful calculation
to tell apart the fall times shown below
during this free fall period of the ongoing natural
progressive structural failure
"....


(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fa0cb7908dee38177e36e60b0cc7d95f6.gif&hash=6f33a99ca916bcba11db979a8f8cf484)

For the 105 foot 2.25 second period of time that we know
the upper part of the building literally fell as a single unit at
gravitational acceleration we know it can not have been
using any of it's potential energy to crush the building
contents, columns and other structural components
beneath it and undergo gravitational acceleration
at the same time (as illustrated by this
frangible impedance scenario)....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F25bd5d8b9f31bb7a59bb3a25fd6f15bd.gif&hash=d1915d878180a829be695bcddf267d74)

It's physically impossible for the lower asymmetrically
damaged part of the building to have naturally progressively
collapsed in any way that could result in the upper part of
the building actually accelerating as it descended symmetrically straight
down through itself as a single unit through the path of maximum
resistance (below right), and then, driven on solely
by gravity, actually continue to accelerate so nearly to
gravitational acceleration (below left) as to require very
careful calculation
for any difference between
the two to be detected....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi.picasion.com%2Fpic78%2F8153c195a283e9e70a635e977539318e.gif&hash=0b1644e11e29d302df35150dfe4c14ff)

Some other force powerful enough to quickly remove all
support
from beneath the upper part of the building as it
descended must be introduced to explain the observed
rate of descent during the 2.25 second period of gravitational
acceleration. For the 2.25 seconds that the building literally fell
at gravitational acceleration, no other force powerful enough to
quickly remove all support from beneath the upper part of the
building was seen to be introduced from outside the building,
and no other force powerful enough to quickly remove all
support
from beneath the upper part of the building is known
to have existed inside the building as an element or normal
function of it's infrastructure. For a load supported by a column
to descend at gravitational acceleration, all support must be
quickly removed, there's absolutely no other way. It must be
knocked out, pulled out, blown out, vaporized etc.
Since no eight story tall boulders were seen rumbling
through Manhatten that day that could have
quickly knocked out all support....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F1663de40a7bf83c865aa619bbf382767.gif&hash=5e1d238515abe6e8ad6f1b98881a8447)

....and no suspicious looking Frenchmen were spotted rigging
for verinage (another form of controlled demolition) the night
before that could have quickly pulled out all support....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic78%2Fc0ac91b333f1ecf2e9ef8388b2182648.gif&hash=b420aa79e76800347650ef34162e188a)

....and no bombs or rockets were seen to be dropped on/fired
at it that could have quickly blown out all support....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic78%2Fa17b1090eba7c867e754cfe3373b5e71.gif&hash=20e82b3512fba6028312b3c48bad2e2b)

....and no giant laser beams or other secret weapons were
being tested in the area that could have quickly
vaporized all support....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic78%2F4d49c47077517a8ea2302b24659a1e00.gif&hash=d2bf4e4834973f7a68d0f6a52981368e)

....and no other force capable of quickly removing all
support from beneath the upper part of the building existed
in the building as a normal function of it's infrastructure (blue)....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic78%2F34be463aa4a4083e6b76ff206a5545d4.gif&hash=3a868bd4ce44385df01082fbb14be3ef)

....it naturally follows that whatever the other force was
that must be introduced to explain the observed 105 foot 2.25
second period of gravitional acceleration of the upper part of the
building as a single unit, it must have been introduced some time
before the event, and unless it can be shown how the other
force
that must be introduced either during or just before
the collapse of the building was introduced from outside
the building, or that it was already existing inside the
building as a normal function of it's infrastructure, the
process of elimination really leaves only one possible
explanation for the building's behaviour. Some energetic
material powerful enough to quickly remove all support
from beneath the upper part of the building during the 105
foot 2.25 second period of gravitational acceleration must
have been physically transported inside the building some
time before the event, it had to be brought in. The
explosion model is the only one....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2Fd09871fcde64ba30384a87220d9837b4.gif&hash=e6217b75adbea43f86f6c9eeb813f68f)

....that can realistically match and empirically be
expected to create the exceptionless condition that
we know must have existed....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic75%2F8db27a83092f9cb1be47bba39ea92628.gif&hash=70fde890e8f9091743cb39d2faa91d2d)

....beneath the literally falling visible upper part of
the building as a single unit during its observed largely
symmetrical descent at gravitational acceleration for
approximately 105 feet in 2.25 seconds....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F0d8f489c42d14f50777e0d8e90059b6a.gif&hash=ec7e55896d81c088b4e19d42f480a2bb)

The undisputed (both the NIST and independent researchers
alike agree) observation of a significant well defined period of
gravitational acceleration of the upper part of the
building as a single unit....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2F6c7cd2005f1c75d081a720e434c5c713.gif&hash=9d9ca0a5d356910efead1c858dd2d6ca)

Stage 1 (0 to 1.75 seconds): acceleration less than
that of gravity (i.e., slower than free fall).

Stage 2 (1.75 to 4.0 seconds): gravitational
acceleration (free fall).
During Stage 2, the north face descended essentially
(displaying all the absolutely necessary, extremely important
features)
in free fall (any motion of a body where gravity
is the only force acting upon it)
, indicating negligible (so
small or unimportant as to be not worth considering)
support
from the structure (approximately 40,000 tons of
structural steel)
below.

 
Stage 3 (4.0 to 5.4 seconds): decreased acceleration, again
less than that of gravity.

(https://web.archive.org/web/20151125150917im_/http://s11.postimg.org/od1nctr3l/oie_animation.gif)

....means that an explosion, or a number of explosions, must
have occurred that was powerful enough to quickly remove all
support
from beneath the upper part of the building (below right),
either all at once or incrementally in advance of its descent,
permitting it to descend at gravitational acceleration as a
single unit for the observed period and under the
exceptionless condition required (below left) for
gravitational acceleration to occur....

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fpicasion.com%2Fpic76%2Fef4a740c36efe88f565475ebbbbf3887.gif&hash=b3f9c7a110be86d92712c2b8561301eb)

The building was brought down by explosives.
Title: Re: What is free fall, and its relation to implosions and building collapse?
Post by: PmbPhy on 17/12/2014 03:09:57
Quote from: Aemilius
Well Bored chemist, your last post makes just as much sense as your first.... none. At least you're consistent!
A very accurate observation.
Title: Re: What is Free Fall?
Post by: jccc on 21/03/2015 08:24:16
free fall is rolling with the punches instantaneously
Title: Re: What is Free Fall?
Post by: Aemilius on 30/04/2015 19:21:43
Chris tells me (privately) that I've had several complaints now so genuine apologies to all for ruffling any feathers (including yours Chris), that was never my intention. From the start all I've really been interested in, all I've really been trying to do, is get to the bottom of it.... and I have now.

Thanks again for engaging me and for helping me sort it out Dr. Calverd, it was a real marathon, and I had fun making the animations too, wouldn't have come up with them otherwise.

I must say though (inhaling deeply) that in view of the overwhelming simplicity of the governing physical principle here involving the Law of Conservation of Energy as applied to a falling body I remain completely baffled as to why there was never any other input by any of the other people here apparently so well qualified to judge the analysis that really should have quickly and naturally led to a simple confirmation or denial by consensus of the veracity of the information conveyed by it as one would normally expect in response to such a fundamentally structured high school level empirically verifiable analysis like this (Reply 143) from such a venerable academic institution as University of Cambridge.... where Isaac Newton himself once held the vaunted Lucasian Chair.

Emile Cole