Elastic vs. Inelastic

An inelastic collisions occurs when two objects collide and do not bounce away from each other.
An elastic collision occurs when the two objects "bounce" apart when they collide.





A car's bumper works by using this principle to prevent damage. In a low speed collision, the kinetic energy is small enough that the bumper can deform and then bounce back, transferring all the energy directly back into motion.





In an elastic collision, both momentum and kinetic energy are conserved.