1. The problem statement, all variables and given/known data 2. Relevant equations K = E + U E = 1/2mv^2 U = mgh 3. The attempt at a solution So I think that for a, half the final velocity of m is equal to the initial velocity of 2m. So that's v = sqrt(2gr)/2? Momentum is not conserved because normal force and gravity are acting on block m correct? Then what do I do from there, and on b and c?