Calculating hang time

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Jan 29th, 2005, 07:43 PM
Dillinger4

Calculating hang time

Ive been trying to figure out how to calculate the hang time of a jumper. Im a bit confused because some of the formulas make no sense to me. One source says that 1/2 the hang time can be calculated with the following formula if the distance is given. t= sqr(2d/g) but wouldn't that use a constant velocity of g not taking into account the extra force exerted for the upward movement?

Just like if somthing is dropped it should fall at a velocity of 9.8m/s² v = gt and if it is thrown down it shoud be v = v_o + gt. So how can this source say that a vertical standing jump of 1.25m = 1sec?
Jan 29th, 2005, 08:34 PM
Phenix

Re: Calculating hang time

If a projectile (i.e a jumper) starts the jump at one altitude (like on the court) and lands at the same altitude (like on the same level court), then the highest point is the half point of the trajectory. So 1/2 the hang time makes sense even though I didn't actually check your formulas.

g is actually an acceleration and is assumed constant over the distance in question.

Actually, the force used at launch equals the force at landing.

And since what goes up (in these projectile problems) usually comes down, it also shows how stupid certain folks can be when they fire bullets in the air at some celebration and later wonder why some innocent gets killed. Sorry, this question reminded me of those kind of folks.
Jan 29th, 2005, 10:31 PM
Dillinger4

Re: Calculating hang time

Quote:

Posted by Phenix

And since what goes up (in these projectile problems) usually comes down, it also shows how stupid certain folks can be when they fire bullets in the air at some celebration and later wonder why some innocent gets killed. Sorry, this question reminded me of those kind of folks.

I guess kinda like getting hit by a penny dropped off the Empire State Building. :lol:
Jan 31st, 2005, 03:06 PM
Phenix

Re: Calculating hang time

Quote:

I guess kinda like getting hit by a penny dropped off the Empire State Building.

In this case, it would be like having a person on the ground throw the penny up to the height of the top of the Empire State building (with whatever force is required for that), and then having that penny come back with the same force.