1. The problem statement, all variables and given/known data Cart 1 on ball-bearing wheels is moving at 4m/sec. It rolls down the hill and hits a stationary cart 2. The collision is elastic. The height of the hill is 1.02 m. Mass of Cart 1: 200 grams; Mass of Cart 2: 400 grams: Find the velocity of cart 1 at point B. 2. Relevant equations m1v1+m2v2=m1v1'+m2v2'; this is all I can think of but I don't have velocity 1 or 2 prime and I'm not sure how to find either of them. I was wondering if I had to use one of the basic kinematic equations because the height of the hill was given, but I'm not sure. 3. The attempt at a solution I have the correct answer (6m/s) , but I would like to know how to do it and I've looked at a couple of kinematic equations with distance in them, but nothing I try seems to work.