Question

A student (m = 68 kg) falls freely from rest and strikes the ground. During the collision with the ground, he comes to rest in a time of 0.04 s. The average force exerted on him by the ground is +18000 N, where the upward direction is taken to be the positive direction. From what height did the student fall? Assume that the only force acting on him during the collision is that due to the ground.

Answer 1

(Average force during impact)*(time)
= (momentum at impact)

Compute the momentum at impact and use the associated velocity V to get the initial height, H.

V = sqrt(2gH)

H = V^2/(2g)

Answer 2

36.824