f4 phy....mechanics

when an object collides with the other, most likely there is sound produced, it implies that the kinetic energy has converted to sound energy....thus almost all the collision on Earth is inelastic. Without any sound, heat produced, the collision is elastic, but it is very rare on Earth....for example, there are five string, each string holds one pinball, if you pick to up and let them swing down from the left, two pinballs will fly up from the right...because the kinetic energy is conserved in this collision. if only one pinball comes up, it means that it is an inelastic collision