# What causes rebounding?

## Main Question or Discussion Point

What causes rebounding?

is my reasoning correct? :
I've come to conclude that when things collide with one another, the force is absorbed by the molecular bonds of the material and depending on the material, either the force causes molecular 'crumpling' like when cars collide, or the force 'stretches' the molecular bonds, which 'snaps back' like a rubber band causing an opposite force that causes the rebound.

http://www.physicsclassroom.com/class/momentum/Lesson-1/Real-World-Applications

The Effect of Rebounding

Occasionally when objects collide, they bounce off each other as opposed to sticking to each other and traveling with the same speed after the collision. Bouncing off each other is known as rebounding. Rebounding involves a change in the direction of an object; the before- and after-collision direction is different. Rebounding was pictured and discussed earlier in Lesson 1. At that time, it was said that rebounding situations are characterized by a large velocity change and a large momentum change.

thanks

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Yes. That is essentially correct. For example in an elastic collision kinetic energy is conserved; during the collision the colliding bodies deform, storing elastic potential energy, and then release the potential energy as they separate. During inelastic collisions the kinetic energy is 'lost' to other forms of energy like thermal energy.

DaveC426913
Gold Member
Yes, what you're talking about is elastic collisions versus inelastic collisions.

Elastic collisions occur when the material can absorb the energy and re-emit almost all of it. Most things do this, including really hard things like billiard balls.
Inelastic collisions occur when the kinetic energy is absorbed by deformation, like cars or like globs of putty.