Question

What is meant by "elastic collisions"?

Answer 1

Well you know how a rubber band is elastic? It sort of just bounces back. Similarly, an elastic collision is one where you have the objects bounce apart. An inelastic collision is just a collision that's not elastic. Like dropping mashed potatoes on the carpet. The mashed potatoes don't bounce after they hit, they just splat.

Answer 2

Better answer - An elastic collision is one in which momentum and kinetic energy are both conserved. In an inelastic collision momentum is conserved but kinetic energy is not conserved.