1. The problem statement, all variables and given/known data You have a horizontal spring system such that it undergoes SHO on a frictionless surface. with a known mass attached at the end of the spring. When that mass reaches its maximum position (amplitude) a second identical mass is dropped on top of the initial, effectively doubling the mass of the system (all other mass shall be considered negligible). What is the amplitude of the new system? 3. The attempt at a solution The same as before? When the initial mass is at its amplitude position, it has all its energy stored as potential energy which does not depend on mass. Therefore, adding mass will not affect this potential energy and thus won't affect amplitude. Is this right?