A 70 kg man just before contact with the ground has a speed of 5 m/s In a stiff-legged landing he comes to a halt in 7ms (miliseconds). Keeping in mind that the average net force acting on the man includes both the force of the ground on the man and the gravity force, find the force of the ground on the man.
force= mg+ma
but a= changevelocity/time=5m/s /.007s