2. Momentum Webster’s: A property of a moving body that determines the length of time required to bring it to rest when under the action of a constant force or moment. “Moving Inertia”

3. What Quantities determine how hard it is to stop an object? Mass Velocity

4. Which of the following has the most momentum? a)A person jogging down the street. b)A Volkswagen Bug traveling down the road. c)A Hummer parked at the mall. d)A freight train at the station.

5. p = mv m = mass (kg) v = velocity (m/s) p = momentum ( kgm/s = Ns) momentum is a vector quantity, it has magnitude and direction. Pay attention to directions!!!!!!

6. Rewriting Newton’s 2 nd Law

7. An impulse is a change in momentum, which is caused by applying a force for a period of time. picture

8. Graphically: The area of a force vs. t graph is equal to the impulse or the  p. F(N) t(s) impulse  p

9. The same  p can be produced by applying a large force for a short time or a small force for a long time  p = F t F t

10. Example 1: A net force of 8N acts on a 200g object for a period of 5s. (a) What is the change in momentum? (b) Assuming the object starts from rest what is its final velocity after 5 seconds?

11. a) b)

12. Example 2: A 300g ball strikes a wall horizontally with a speed of 25m/s and bounces straight back with a speed of 15m/s. The ball is in contact with the wall for 5x10 -3 s. What average force does the wall apply to the ball? 25m/s 15m/s

14. Example 3: The following graph represents the net force applied to a 5kg object vs. the time the force is applied. Find the final velocity of the object if the original velocity was 12m/s. 50Ns 100Ns

15. area = impulse =  p