1. The problem statement, all variables and given/known data After falling from rest at a height of 30m, a 0.50 kg ball rebounds upward, reaching a height of 20m. If the contact between ball and ground lasted 2.0 ms, what a average force was exerted on the ball? 2. Relevant equations The kinematic equations? F=ma w=mg? I dont really know 3. The attempt at a solution Sorry I don't even know where to begin. I don't really understand this section in the book so i dont even know what to do. The answer is supposed to come out to 1.1 x 10^4 upward.