20 points: how can you tell if momentum is conserved in both elastic and inelastic conditions?

Describe uniform velocity and variable velocity in short

Anybody wanna ? (picture included? )

When you jump from an elevated position you usually bend your knees upon reaching the ground. by doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. in this way the average force your body experiences is a) less than 1/10 as great. b) more than 1/10 as great. c) about 1/10 as great.d) about 10 times as great.