1. The problem statement, all variables and given/known data I came with this problem myself, so there may be not enough information given to solve it. Imagine that mass M oscillating on the vertical spring with force constant k and amplitude A. Now lets say that the mass M is moving upward. Now imagine that some other object with mass m having speed v_m comes from the sky and collides with the oscillating mass and after collision sticks to it. 2. Relevant equations Is it possible stop the mass M from oscillation? What position? What velocity of v_m? 3. The attempt at a solution Can I apply conservation of momentum at every displacement of the spring assuming it happen in short time? Applying it at equilibrium position would give: v_s*M - v_m*m = 0, where v_s is the speed of the mass M. But does the final momentum equal to zero means that both bodies stuck and do not move or that they exchanged momentum and still moving to opposite directions?