this problem came up in my mcat physics prep book. two masses, one twice as massive as the other, are placed on a platform atop a spring. when they're launched, what height do they achieve? i know they reach the same height, and from a previously archived thread on this board, i understand (somewhat) the reason.. the elastic potential energy is first transformed to kinetic energy, which is then transformed to gravitational potential energy. equating the formulas for those two energies results in an expression that is independent of mass. what confuses me is that this seems to imply that the height of a mass launched by a spring is independent of mass altogether. this is clearly false.. could someone explain why?