1. The problem statement, all variables and given/known data Ball A at rest is dropped from a height H and ball B at the same time is thrown up from the ground. When they collide at height h, the velocity of ball A is twice the velocity of ball B. What is h/H? 2. Relevant equations 1D Kinematics 3. The attempt at a solution I have no idea which of these equations to use, even when I list all of my knowns and what I can infer from this. I just randomly pick every single equation and try to plug everything in because it all looks about the same to me. So for ball A: (Initial velocity) V_0 = 0 m/s (Final velocity @ collision) V_A = -(2V_B) (negative velocity because it's going downwards) g = -9.8 m/s^2 (displacement) x - x_0 = h - H ball B: (Initial velocity)V_0 = ? (Final velocity @ collision) V_B = |(V_A)/2| (positive velocity because going upward) g = -9.8 m/s^2 x - x_0 = h And t_A = t_B since the same amount of time elapses when they both collide since they were released at the same time. I tried plugging in for the equations and got all these nonsensical statements that I have no idea what they mean. I got stuff like V_0 of B = -9.8t but I don't know if that's useful. Also -19.6t = 19.6h + 19.6H and a bunch of other stuff I have no clue if is meaninful or not.