Question

Stand flatfooted next to a wall and mark the highest point you can reach. Then jump vertically and mark the highest point. The distance between the marks is your vertical jumping distance. Use this to calculate your hang time.

Answer 1

I don't need to know my hang time. If you need to know it for yourself, just follow the directions. Surely you have some kind of time measurement.

Answer 2

If you assume the body is stretched similarly, with one arm upward, before, at the peak of and at the end of the jump, then the vertical jumping distance can be related to hang time. This is not the way most people would jump. The foot-to-center-of mass-distance has to remain the same if the calculation of hang time from jumping distance is to be accurate.

If X is the vertical jumping distance,
X = (1/2)g (T/2)^2
where T is the hang time. T/2 is the time it takes to fall back down.
T^2 = 8X/g
T = sqrt (8X/g)