1. The problem statement, all variables and given/known data I was asked to compare the energy loss of a system of two boxes moving towards each other, colliding elastically and in-elastically in two different situations that are not influenced by friction. There are no springs attached to either mass 3. The attempt at a solution I believe the magnitude of the energy lost in the inelastic collision is more than that of the energy lost in an elastic collision undergoing no net external force, is energy loss due to internal forces in these situations? I believe there is no change in kinetic energy or momentum in an elastic collision while there is a change in the kinetic energy of the system in an inelastic collision but no change in momentum in this case. How is energy lost if there is no deformation of the material? No heat generated by the collision? Could sound really give off all that energy? I'm not sure, thank you for your time.