[alancalverd]

"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!

[Aemilius (OP)]

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.

Before I make any more animations.... Is this an acceptable schematic format? 

[alancalverd]

I think we have agreed on the definition of free fall. No need for animations, but I'm impressed with yours.

[Aemilius (OP)]

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?

[Aemilius (OP)]

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....

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....

Is that acceptable?

[alancalverd]

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!

[Aemilius (OP)]

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.

[Aemilius (OP)]

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.

[Aemilius (OP)]

I synchronized the animations (reply 24).

[alancalverd]

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.

[Aemilius (OP)]

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?

[alancalverd]

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..."

[Aemilius (OP)]

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....

"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!

[alancalverd]

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.

[Aemilius (OP)]

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! 

[Aemilius (OP)]

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).

[Aemilius (OP)]

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.

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....

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....

[Aemilius (OP)]

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.

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....

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....

[alancalverd]

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.

[RD]

... 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 will do inbetweening ...

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