This document discusses momentum, impulse, and angular momentum. It begins by defining momentum and impulse, and how to calculate impulse from force and time. It then discusses how momentum and impulse are vectors and how their directions are important. Examples are given of calculating momentum and impulse in situations like hitting a baseball or stopping a moving vehicle. The document also introduces angular momentum and how torque is required to change angular velocity. Homework problems are assigned at the end to further understanding of these concepts.

1. Chapter 9

2. Impulse and Momentum
• How do I define momentum?
• How do I determine the impulse given to an object?
• How do I define the angular momentum of an object?

3. Newton’s Second Law
• F = ma
• Dropping a book
• Does the F = ma help us?
• Hitting a ball?

4. Momentum

5. Momentum
http://www.youtube.com/watch?v=y2Gb4NIv0Xg

6. Impulse

7. Impulse

8. Impulse and Momentum
• If the force on an object is constant, the impulse is the product of the
force multiplied by the time interval over which it acts
• Because velocity is a vector, momentum is also a vector
• Similarly, impulse is a vector because force is a vector
• This means signs will be important for motion in one dimension

9. Baseball Being Hit
• Impulse is the area under the Force
time curve
• For this example, impulse N·s
• Direction?
• Area = impulse = 13.1 N·s

10. After the ball has been hit?
m = 0.145 kg
v = -38 m/s
Impulse = 13.1 N·s
Final momentum?
Final speed?

11. Example
A 2200 kg vehicle traveling at 94 km/h can
in be stopped in 21 s by gently applying
the brakes. It can be stopped in 3.8 s if
the driver slams on the brakes, or in 0.22 s
if it hits a concrete wall. What average
force is exerted on the vechicle in each of
the stops?

12. Applications
• What happens to the driver when a crash suddenly stops a car?
• An impulse is needed to bring the drivers momentum to zero
• A large change in momentum occurs only when there is a large impulse
• A large impulse can result either from a large force acting over a short
period of time or from a smaller force acting over a long period of time
• Air bag
• Bending legs when you jump

13. Angular Momentum
• We can also talk about momentum for angular motion
• Angular velocity only changes if a torque is applied
• Spinning?

14. Homework
Read Section 9.1
Do Problems # 1 – 9, starting page 233

15. Car Crashes

16. Egg Drop

17. Homework
Page 251, # 56 - 66