1. Chapter 8: Momentum P=mv

2. Momentum is conserved for all collisions as long as external forces don’t interfere.

3. What is Momentum? momentum = mass X velocity Momentum is a vector We represent momentum with the letter p Question: What are the ways that an object can have a large momentum (p)? Answer: A moving object can have a large momentum if it has a large mass, a high speed, or both.

4. A Change in momentum is an acceleration. Question: What makes an object change momentum? Answer: A net force applied to the object will change the object’s momentum. Question: Does the longer the force is applied to an object effect the object’s motion? Answer: Yes. The longer the force is applied the more the object’s velocity and thus momentum will change.

5. To Summarize A change in momentum Depends on the force that acts on the object and the length of time the force acts. We have a name for this. Change in momentum = impulse Impulse = force X Time

6. Impulse. Impulse = force X time

7. Bouncing Think about the change in momentum to stop an object. The impulse required to bring an object to a stop and then to throw it back again is greater than the impulse required merely to bring the object to a stop.

8. Conservation of Momentum The total momentum of a system before and after an event does not change.

9. Collisions Elastic Collision - When objects collide without changing shape. Inelastic Collision - A collision in which the colliding objects change shape.

10. Example: Inelastic Collision Beware! Math ahead. Look at the example of two train cars colliding. Once they collide, they become one.