Question

What makes some collisions elastic and others inelastic?

Answer 1

A perfect elastic collision is defined as one in which there is no loss of kinetic energy in the collision. An inelastic collision is one in which part of the kinetic energy is changed into another form of energy in the collision. Well hope this answers your question :)

Answer 2

Nature of matter makes is elastic or inelastic. Two sponge balls collision would be inelastic. Two still balls collision would be inelastic.