An elastic collision is a collision where there is no loss of kinetic energy. Therefore, it can be said that, since KE is conserved, momentum is conserved. In other words the momentum and total kinetic energy before and after the collision are the same. An example of an elastic collision is the movement of swinging balls. Whereas, in an inelastic collision some kinetic energy is changed to another form of energy such as heat or sound. Therefore in an inelastic collision, energy is not conserved. An example of this of an inelastic collision is a car crash.