Notes: Chapter 11.3 Newton’s Third Law of Motion and Momentum

1. Notes: Chapter 11.3 Newton’s Third Law of Motion and Momentum

2. Newton’s Third Law of Motion • For every action force there is an equal and opposite reaction force. • Called force pairsor action/reaction pairs • Force pairs do not act onthe same object, and thus don’t always have the same effect! • Movie: Newton's third

3. Newton’s Third Law of Motion • The equal forces don’t always have the same effect, though. • According to the second law, F=ma. You will have different results depending on their masses.

4. Momentum • An extension of Newton’s Third Law…tells what will happen from the action/reaction • Is equal to mass x velocity • p = mv • units have no name, just kg . m/s

5. Momentum & Collisions • In collisions, momentum is conserved for the system(both balls), that is, it is the same for all the objects before and after the collision. • Called The Law of Conservation of Momentum

6. Law of Conservation of Momentum • The system is both of the pool balls. If they have the same mass: • the total momentum before is mv + m0= mv • the total momentum after is m0 + mv = mv

7. Law of Conservation of Momentum • What if the red ball has twice the mass of the white one? How fast will it move? • What if the white ball has twice the mass of the red one? How fast will it move?

8. Momentum & Collisions • Elastic collision: objects hit each other and don’t stick together (bounce off) • Inelastic collision: objects hit each other and stick together • Momentum and Collisions • Conservation of Momentum