Average force is change in momentum, divided by change in time, correct? So when I land on the ground after jumping, how can I calculate the average force I exert on the ground, (while I decelerate from velocity at moment I touch ground to zero velocity). I calculated my velocity just when I touch ground. Clearly my final is zero, so my change in momentum is just my initial velocity times my mass. Divide this by the time taken, found from initial velocity and acceleration, and I should get average force, right? But it doesnt work out to the value I should get. Am I going wrong in my idea here? Should I be doing it a different way???