PHY 2048C General Physics I with lab Spring 2011 CRNs 11154, 11161 & 11165

1. PHY 2048CGeneral Physics I with labSpring 2011CRNs 11154, 11161 & 11165 Dr. Derrick Boucher Assoc. Prof. of Physics Session 10, Chapter 9

2. Chapter 9 HomeworkDue Friday @ midnight

3. Chapter 9Practice Problems 11, 23, 25, 29, 31, 35, 39, 55 Unless otherwise indicated, all practice material is from the “Exercises and Problems” section at the end of the chapter. (Not “Questions.”)

4. Example, Problem 9-8, p. 262

5. Impulse and Momentum Momentum is the product of a particle’s mass and velocity, has units of kg m/s, and is given by The impulse upon a particle is defined as Impulse has units of N s, but you should be able to show that N s are equivalent to kg m/s. The impulse-momentum theorem is

7. EXAMPLE 9.2 A bouncing ball QUESTION:

8. EXAMPLE 9.2 A bouncing ball

9. EXAMPLE 9.2 A bouncing ball

10. EXAMPLE 9.2 A bouncing ball

11. EXAMPLE 9.2 A bouncing ball

12. EXAMPLE 9.2 A bouncing ball

13. EXAMPLE 9.2 A bouncing ball

14. Example, Problem 9-8, p. 262

15. Conservation of Momentum

16. Conservation of Momentum Stated mathematically, the law of conservation of momentum for an isolated system is The total momentum after an interaction is equal to the total momentum before the interaction.

17. Example, Problem 9-18, p. 263

18. Conservation of Momentum Depends on the System

19. Conservation of Momentum Depends on the System

21. Problem-Solving Strategy: Conservation of Momentum TWO (or more) DIMENSIONS

22. Example, Problem (made-up)

23. Chapter 9. Clicker Questions

24. The cart’s change of momentum is • 30 kg m/s. • 10 kg m/s. • –10 kg m/s. • –20 kg m/s. • –30 kg m/s.

25. A 10 g rubber ball and a 10 g clay ball are thrown at a wall with equal speeds. The rubber ball bounces, the clay ball sticks. Which ball exerts a larger impulse on the wall? • They exert equal impulses because  they have equal momenta. • The clay ball exerts a larger impulse  because it sticks. • Neither exerts an impulse on the wall  because the wall doesn’t move. • The rubber ball exerts a larger  impulse because it bounces.

26. Objects A and C are made of different materials, with different “springiness,” but they have the same mass and are initially at rest. When ball B collides with object A, the ball ends up at rest. When ball B is thrown with the same speed and collides with object C, the ball rebounds to the left. Compare the velocities of A and C after the collisions. Is vA greater than, equal to, or less than vC? • vA > vC • vA < vC • vA = vC

27. The two particles are both moving to the right. Particle 1 catches up with particle 2 and collides with it. The particles stick together and continue on with velocity vf. Which of these statements is true? • vf = v2. • vf is less than v2. • vf is greater than v2, but less thanv1. • vf = v1. • vf is greater than v1.

28. An explosion in a rigid pipe shoots out three pieces. A 6 g piece comes out the right end. A 4 g piece comes out the left end with twice the speed of the 6 g piece. From which end does the third piece emerge? • Right end • Left end