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# Types of Collisions

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## Types of Collisions

**There are 3 types of collision that you need to know about at A-level...**

**(A special case)**

- All momentum is conserved (not surprisingly - it always is!)
- Kinetic energy
**is**conserved (that's what makes this special). - Relative speed of approach = relative speed of separation.

(So if one is catching the other at 10m/s before the collision, it will be moving apart from it at 10m/s after the collision).

**Perfectly Elastic** collisions are surprisingly common. All collisions between atoms are Perfectly Elastic according to the Kinetic Theory of Gases.

**(Another special one)**

- All momentum is conserved (as always).
- Kinetic energy is
**not**conserved. - The relative speed of separation is zero.

**(The usual old case)**

- All momentum is conserved (again).
- Kinetic energy is not conserved (again).
- You can't say anything about the speed at which they leave each other without doing a calculation.