1. The problem statement, all variables and given/known data After falling from rest at a height of 29.8 m, a 0.422 kg ball rebounds upward, reaching a height of 21.7 m. If the contact between ball and ground lasted 1.83 ms, what average force was exerted on the ball? 2. Relevant equations Change in momentum (p) = Fnet* Change in Time FGrav=m*g Delta y = Vavg,y*Change in Time 3. The attempt at a solution I understand all of these formulas, but I am not quite sure where the 1.83 ms goes as far as which time it is actually describing in a specific formula. I know that the average velocity on the way down is actually just the final velocity divided by 2, since the initial velocity is 0... I feel like I'm on the brink of solving this but I'm not quite sure where to go next.. Thanks!