1. Conservation
Collisions

2. Conservation of Linear Momentum
The change in momentum of a system is equal to the impulse put on the system.

3. Conservation of Linear Momentum
For example: Jeff Bagwell hits a baseball…
Initially

4. Conservation of Linear Momentum
For example: Jeff Bagwell hits a baseball…
During hit

5. Conservation of Linear Momentum
For example: Jeff Bagwell hits a baseball…
Finally

6. Two types of collisions
Elastic:
The objects do not stick together or change shape.
Momentum and kinetic energy are conserved.
Inelastic:
The objects do stick together and/or change shape.
Only momentum is conserved!

7. Example of an elastic collision
The cue ball hits two billiard balls initially at rest on a billiard table. Assume that the cue ball stops after hitting the other balls. What is the final velocity of the red and blue ball? y θ x

8. y θ x

9. y θ x

10. y θ x We have three equations and four unknowns.
We cannot solve this problem without more information.
You will usually be given the speed or angle of one of the balls.