Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: paul.fr on 23/11/2008 20:42:15
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Two skydivers jump out of a plane, at the same time, and have forgotten their parachutes. One of them throws out the contents of his pockets, one by one. First the anvil, then the tennis ball and lastly his last £1 coin. In what order do they all hit the ground (men and objects)?
Edit:
both skydivers weigh the same...say 15 stone.
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Anvil first - least drag for a given weight.
Tennis ball last.
Man with full pockets before man with empty pockets
Throw me a lot of pound coins and I'll do the experiment. I'm not sure of the drag for a coin.
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Throw me a lot of pound coins and I'll do the experiment. I'm not sure of the drag for a coin.
[;D]
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Drag for a coin very great indeed - terminal velocity around 70kph.
Otherwise I agree with the previous analysis - anvil first and tennis ball last. Two skydivers will hit the ground around the same time (mass is not important - only drag).
PS - edit - dumb of me to say mass is not important [>:(] I meant to say ratio of mass/drag is important
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I disagree about both skydivers hitting the ground about the same time, the one whose pockets still contain an anvil although his drag will be increased by the bulge thereof will certainly get down first.
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terminal speed is set when drag equals weight
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Well, assuming no 'buoyancy' effect, we have:
Vt=√(2.m.g/(ρ.A.C))
Where Vt is terminal velocity, m = mass, g = gravity (9.81 ish), ρ = density of air, A is area of object, C is coefficient of drag
Obviously the important factors for our 2 skydivers will be mass and coefficient of drag (given all other factors should be roughly equal).
The question is, therefore, does the increased mass 'overpower' the loss of streamlining and subsequent increase in C? Simple answer is I don't know [;)]
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I admit it's a matter of degree but 'anvil' implies a similar weight of steel to the weight of the jumper and a small increase in volume (anvils tend to be compact - see loony tunes!). In that case, the outcome is fairly predictable.
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I admit it's a matter of degree but 'anvil' implies a similar weight of steel to the weight of the jumper and a small increase in volume (anvils tend to be compact - see loony tunes!). In that case, the outcome is fairly predictable.
Agreed, but the possibility of someone walking around with an anvil in their pocket struck me as rather remote and I therefore assumed we might be talking about something rather less massive [;)]
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I suppose I would be wrong to refer you to the original post.
Sorry :-)
(Big pockets)
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Well, the OP might have meant a really tiny anvil used to shoe ants [;)]
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Or an anvil of change? (Say it)
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Or an anvil of change? (Say it)
****!
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It's the way I tell em.
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(anvils tend to be compact - see loony tunes!)
You noticed the "clever" way i substituted Wile E. Coyote for two skydivers.
Agreed, but the possibility of someone walking around with an anvil in their pocket struck me as rather remote and I therefore assumed we might be talking about something rather less massive [;)]
Never imagine there to be any thought behind the question.
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The sky divers are obviously time lords as they have TARDIS pockets.
I disagree about both skydivers hitting the ground about the same time, the one whose pockets still contain an anvil although his drag will be increased by the bulge thereof will certainly get down first.
I think the bulge might be to do with fear! Is that an anvil in your pocket or are you just pleased to see me?
I think if the anvil sticks out enough then this WILL slow the man down. If he is a time lord and the anvil doesn't spoil the crease of his trousers then he will hit the floor at the same time as the other guy, unless of course, someone puts an acme roll out hole under said man.