1. The problem statement, all variables and given/known data Is more work done on a large or a small mass? 2. Relevant equations F = d/dt (mv) W = Fd 3. The attempt at a solution Greater the mass, greater the velocity according to F = d/dt (mv) If the problem is given that one asks this given question, should one consider that, since motion only exists in the x-direction, so the mass is an independent clause? Does this sounds right? I mean in momentum, when a small mass hits a larger mass, we see the smaller mass moves at a greater velocity, assuming it is elastics. However, when I look at W = E (mechanical energy) and KE, if the system is conservated with no external force, we always cancel out m (mass). But how come the answer is "no difference"?