IF you throw metal or wood or whatever material ball into soft bed then it almost do not reflecting from bed as you can try. So where goes such ball momentum and kinetic energy? Need to solve such collision problem. Metal ball of mass 1 kg moving at velocity 100 m/s hit not moving bed and hit into soft side of bed into center of bed. Bed mass is 40 kg. And in another collision variant the same ball mass of 1 kg moving at 100 m/s hit metal box (box is not empty but all filled with metal or just another ball) of mass 40 kg into center. What would be velocity of bed and of metal box after collision. Or more simple: is velocities will be same of bed and box or different? Because if ball very weakly reflecting from bed soft part then maybe it means that ball to bed giving more of his momentum or kinetic energy?