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Author Topic: If I fall from an Airplane, I die.. What if I chuck an ANT?  (Read 13725 times)

Offline Seany

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If I fall from an Airplane, I die.. What if I chuck an ANT?
« Reply #25 on: 12/04/2007 16:27:53 »
But how can you assume that a drop from a table top for an ant is not rare for an ant?

After all, that is like 1000x taller than their height. And ants live in a 2-Dimensional world unlike humans in a 3-Dimensional world. Surely ants aren't used to being "dropped" ?
 

another_someone

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If I fall from an Airplane, I die.. What if I chuck an ANT?
« Reply #26 on: 12/04/2007 17:27:36 »
Actually, ants don't live at all in a 2 dimentional world - they crawl over all sorts of things, and generally are good climbers - but what goes up, must come down, and sometimes precipitouslly.

There are almost 12,000 species of ant, so one has to ofcourse be careful about making any statement that is true of them all, but certainly, I have often seen ants crawling along table tops, and sometimes will fall off the edge.

http://en.wikipedia.org/wiki/Ant
 

Offline Seany

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If I fall from an Airplane, I die.. What if I chuck an ANT?
« Reply #27 on: 12/04/2007 17:30:37 »
MM lol thanks. Are you sure they didn't die falling off the table edge? :P
 

Offline Bored chemist

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If I fall from an Airplane, I die.. What if I chuck an ANT?
« Reply #28 on: 12/04/2007 19:31:10 »
OK, so it's not just physicists who calculate absurd assumptions like the free fall speed of spherical ants; Bored Chemists do it too.
This page
http://en.wikipedia.org/wiki/Stokes'_law
tells you what the formula is for the terminal velocity (under a set of assumptions that may not be true here).
The terminal speed increases with the square of the radius.
Since I could roll up into a ball about half a metre across and an ant could bundle itself into half a centimetre we are talking about a radius ratio of about 100 to 1. That makes the terminal velocity for the ant about 1/10000 of mine.
120MPH is about 53m/sec (this makes no real difference but converting it into metric makes it look more scientific)  ;D.
So our ant should fall at half a centimetre per second. OK it looks like that's a bit low to me, but I did say I was making some assumptions.

There's another big matter to look at here. Ants and people are held together with exoskeletons, ligaments and stuff. All those are, in turn held together by chemical bonds of some sort. Breaking me or the ant needs energy in order to disrupt those chemical bonds.
At 53m/s every kilo of me carries about 1400 Joules of kinetic energy.
Each Kg (OK, I know ants don't weigh 1 kilo) of the ant at 0.053 m/sec carries just 0.0014 Joules.
 When we hit the ground the ant has a lot less energy to dissipate than I do. That's why it survives. The splat per unit weight varies as the fourth power of the radius. (It's not often you see 4th order terms in real life)
I think a typical cat is about 5 kilos in weight; a typical human is about 70 so a cat weighs roughly 0.07 times as much. If we assume the same shape and density (which is absurd, but it's as good an approximation as I can think of) it must be about 0.4 times as big as a person. (That would mean that compared to a spreadeagled human who cover about 2 metres diameter a cat would be about 0.8 metres front paw to opposite back paw which seems a bit big) If that's true then, at terminal velocity, it possesses about 3% of the stored energy of a falling human. If the cat's smaller than that it does even better. I think that may have more to do with cats' survival than their fur (though the fur must help).
Similarly you can look at the few people who have survived falling from planes without parachutes; they generally landed in trees or snow (or both). In this way the energy was dissipated by breaking twigs and squashing snow rather than by the body.
« Last Edit: 12/04/2007 19:34:27 by Bored chemist »
 

another_someone

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If I fall from an Airplane, I die.. What if I chuck an ANT?
« Reply #29 on: 12/04/2007 20:38:21 »
So our ant should fall at half a centimetre per second. OK it looks like that's a bit low to me, but I did say I was making some assumptions.

1/2 cm/sec. (not even SI, but CGS units :)) amounts to about 30cm per minute, or about a foot per minute.  From 30,000 feet, that is 30,000 minutes to reach the surface, or just under 8 hours.

Not that I actually thing 1 foot per minute (about 1/100thmph) is a credible speed - so from a table top that is 3 foot off the ground, it should take 3 minutes to reach ground to reach the ground (this is not even allowing for the time to accelerate to terminal velocity).  Last time I saw an ant drop from that height, I did not recall having to wait that long for it to reach the ground.
« Last Edit: 12/04/2007 20:46:22 by another_someone »
 

Offline Seany

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If I fall from an Airplane, I die.. What if I chuck an ANT?
« Reply #30 on: 12/04/2007 20:56:52 »
Lol anyway Bored Chemist, thanks alot for that, now I understand why it wouldn't die. Because of the energy which the ant has is so much lower than that of a human.

So is there no way that an ant can die, from falling?
 

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If I fall from an Airplane, I die.. What if I chuck an ANT?
« Reply #30 on: 12/04/2007 20:56:52 »

 

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