Original question: Two people (each of mass m) are standing on the stern of a boat of mass M. Ignoring friction, find the boat’s velocity v after they jump out with a horizontal velocity u relative to the boat’s initial velocity (a) if they jump together (b) if they jump one after another (c) which velocity is greater? I followed the path of using equal total momentum before and after to solve the problem, and I just but for some reason, my (a) velocity expression is greater than my (b) velocity expression. Is this supposed to happen? I assumed this is like a multi-stage system, where final velocity should be higher if there are more stages. My set up is (M+2m)vi = 2m(vi - u) + M(vf) where vi is initial velocity of boat and vf is final (what im looking for) (vi - u) would be velocity of the two people relative to water.. right?