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  4. How far from the building should the professor be when you release the egg?
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How far from the building should the professor be when you release the egg?

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Online Bored chemist

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Re: How far from the building should the professor be when you release the egg?
« Reply #20 on: 18/12/2021 00:56:35 »
Quote from: Petrochemicals on 17/12/2021 23:31:17
Quote from: alancalverd on 17/12/2021 23:14:38
Quote from: Bored chemist on 17/12/2021 09:06:49
I'm sure that both of us have sat in an exam or schoolroom and made calculations assuming free fall conditions (Knowing that if we tried to "show off" and include it, we would get the wrong answer) without asphyxia.

Why would it be different now?
. Youngsters may have seen experiments in free fall where the ambient air was also in free fall, in planes and spacecraft, and some pensioners will recall seeing a hammer and feather in free fall towards the moon.
I imagine if you dropped a feather at the edge of a tall build g it would immediatley rise due to the upward air effects.
Like a stopped clock, even Petrochemicals is occasionally right, and I think this may be one of them.
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Re: How far from the building should the professor be when you release the egg?
« Reply #21 on: 18/12/2021 11:25:11 »
Quote from: Bored chemist on 18/12/2021 00:53:46
If my memory serves me, it's called "departure from rubric",
I wonder how often you called it into play (presumably unknowingly).
Once, knowingly, during a viva.  The examiner got very interested, the exam overran, and we ended up with a publication.
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Re: How far from the building should the professor be when you release the egg?
« Reply #22 on: 18/12/2021 11:40:53 »
As for air blowing up the side of a tall building, what goes up must come down, so whether the feather rises or falls depends on the wind direction. Large birds and skilled glider pilots are very good at soaring on the windward side but the air downwind is best avoided: there's a turbulent "rotor" close to the structure and possibly a smooth downdraft a little  further back. The smooth wave can often be detected at 5 times the height of the obstruction. 

Anyway, if we drop an egg it will take about 3 seconds to reach the prof's head in vacuo (the ambient, not the prof's head). If we use a small egg, with a large surface/mass ratio, and real air, we might be looking at 5 seconds fall time, which could result in a considerable lateral displacement if there is any wind. The gentlest of breezes (1 m/s, 2 mph) would pretty well guarantee a miss first time. Which is why it takes 6 months to turn a competent marksman into a reliable sniper. 
« Last Edit: 18/12/2021 11:44:08 by alancalverd »
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Online hamdani yusuf

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Re: How far from the building should the professor be when you release the egg?
« Reply #23 on: 19/12/2021 07:40:22 »
Quote from: Bored chemist on 17/12/2021 19:45:41
Quote from: Origin on 17/12/2021 18:32:47
Quote from: hamdani yusuf on 17/12/2021 12:39:28
The answer could be quantized if this statement is replaced with walking toward the building (assuming there's an open door to go through).
Huh?
I don't think "quantized" is the right word.
But it could be made into a more sensible maths problem by making that assumption.
Perhaps the word "quantified" is more appropriate here.
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Re: How far from the building should the professor be when you release the egg?
« Reply #24 on: 19/12/2021 11:09:10 »
Throw lots of eggs, observe how each one falls and correct for the extent by which you miss.
There's not much the prof can do about it until he gets into the building, or escapes beyond your reach.

That's why the military always like "the high ground".
Beware of professors with umbrellas or mobile phones.

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Re: How far from the building should the professor be when you release the egg?
« Reply #25 on: 19/12/2021 11:59:31 »
Stories of long sniper kills mostly have a maximum of 3 shots - the target tends to get suspicious after the second one. To quote James Bond: "Once is happenstance. Twice is coincidence. Three times is enemy action."

So set yourself up with an anemometer and wind vane (physics) rather than a bucket of eggs (engineering). Add a stopwatch if you are using small eggs.

And don't presume that the professor is male - you can get into serious trouble for using the word "he" these  days.
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Re: How far from the building should the professor be when you release the egg?
« Reply #26 on: 19/12/2021 12:19:05 »
Quote from: alancalverd on 19/12/2021 11:59:31
And don't presume that the professor is male - you can get into serious trouble for using the word "he" these  days.
I didn't "assume" it; I deduced it from.
"Your physics professor, who is 1.80 tall".
I'm not saying that's a perfect proof, but it gave me enough evidence to call it on the balance of probabilities.

Quote from: alancalverd on 19/12/2021 11:59:31
Stories of long sniper kills mostly...
... are irrelevant if you are effectively using a machine gun.
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Re: How far from the building should the professor be when you release the egg?
« Reply #27 on: 19/12/2021 12:19:56 »
Quote from: alancalverd on 19/12/2021 11:59:31
To quote James Bond: "Once is happenstance. Twice is coincidence. Three times is enemy action."
It was said to Bond, not by him.
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Re: How far from the building should the professor be when you release the egg?
« Reply #28 on: 19/12/2021 14:29:18 »
If you are using a machine gun, you don't usually
Quote from: Bored chemist on 19/12/2021 11:09:10
observe how each one falls
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Re: How far from the building should the professor be when you release the egg?
« Reply #29 on: 19/12/2021 14:45:48 »
Quote from: alancalverd on 19/12/2021 14:29:18
If you are using a machine gun, you don't usually
Quote from: Bored chemist on 19/12/2021 11:09:10
observe how each one falls

https://en.wikipedia.org/wiki/Tracer_ammunition
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Re: How far from the building should the professor be when you release the egg?
« Reply #30 on: 19/12/2021 19:01:18 »
The equations that Alan quotes are a good approximation for bodies falling a few hundred meters but would only be accurate if the Earth was flat and of infinite extent.
As the distance from the centre of the Earth increases the force of gravity falls off otherwise the bodies would tend to acquire infinite energy !
These equations caused me considerably confusion when they were first foisted on me at school but I know better now   
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Re: How far from the building should the professor be when you release the egg?
« Reply #31 on: 19/12/2021 19:23:59 »
Quote from: syhprum on 19/12/2021 19:01:18
The equations that Alan quotes are a good approximation for bodies falling a few hundred meters but would only be accurate if the Earth was flat and of infinite extent.
As the distance from the centre of the Earth increases the force of gravity falls off otherwise the bodies would tend to acquire infinite energy !
These equations caused me considerably confusion when they were first foisted on me at school but I know better now   
was Jules Verne  your physics teacher?
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Re: How far from the building should the professor be when you release the egg?
« Reply #32 on: 20/12/2021 11:31:08 »
Quote from: Bored chemist on 19/12/2021 14:45:48
https://en.wikipedia.org/wiki/Tracer_ammunition
So 1 in 5 eggs should have a magnesium shell. I'll have a chat with the chickens.
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Re: How far from the building should the professor be when you release the egg?
« Reply #33 on: 20/12/2021 11:34:30 »
Quote from: syhprum on 19/12/2021 19:01:18
The equations that Alan quotes are a good approximation for bodies falling a few hundred meters but would only be accurate if the Earth was flat and of infinite extent.
No, they are absolute mathematical definitions, nothing to do with gravitation or any other aspect of practical physics. It happens that at 0 - 42m potential difference from the surface of the earth, a = g = constant to a very close approximation.
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Re: How far from the building should the professor be when you release the egg?
« Reply #34 on: 20/12/2021 11:55:06 »
Quote from: alancalverd on 20/12/2021 11:31:08
Quote from: Bored chemist on 19/12/2021 14:45:48
https://en.wikipedia.org/wiki/Tracer_ammunition
So 1 in 5 eggs should have a magnesium shell. I'll have a chat with the chickens.
Good luck with getting them to deliver the eggs at about the speed of sound.
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Re: How far from the building should the professor be when you release the egg?
« Reply #35 on: 21/12/2021 11:07:00 »
Tracer shells are not manufactured by a process that would cause them to ignite in the factory.

You should visit a farm sometime: chickens don't actually squeeze pickled eggs out of their backsides, but you can control various aspects of the egg by breeding and feeding.
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