Can Someone Please explain this problem???

Question

For a movie scene, an 85.0 kg stunt double falls 12.0 m from a building onto a large inflated landing pad. After touching the landing pad surface, it takes her 0.486 s to come to a stop. What is the magnitude of the average net force on her as the landing pad stops her?

Answer 1

Compute her negative acceleration and the net force will be
F=ma

Her speed just before hiting the pad is v=gt
t we ca find from H=.5gt^2
t=sqrt(2H/g)
so v=g sqrt(2H/g)=
v=V2=sqrt(2Hg)

a=(V2-V1)/ts
a=(sqrt(2Hg) -0)/ts where ts=0.486 s

F=ma
F=m(sqrt(2Hg))/ts
F=85.0 sqrt(2x12x9.81)/0.486 =2684 N