Question

A Stone of 5 kg falls from the top of a cliff 50 m high and buries 1m in sand. Find the average resistance offered by the way sand and the time taken to penetrate.

Answer 1

force*distance=energyfromfalling= mgh
force=5*9.8*50/5 N

Answer 2

time:
force*time= mass*changeinvelocity

change in velocity:
1/2 m vf^2=mgh
vf=sqrt(2gh)

time= mass*sqrt(2gh)/forceabove