A student (m = 66 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.

Here is my work. Can't figure out what I am doing wrong.

18000 N => Average force
0.04 s=> Time
66kg => Mass

Average force*time = M*Vf -M*Vo
18000*0.04 = 66*Vf - 66*0
10.91 = Vf

Vf = 2h/t
10.91 = 2h/0.04
h = 0.218

1 answer

Figured it out!

(V impact)^2/(2*g)

V impact = (F ground*t)/m

=6.07 m