1. 10/01/2013PHY 113 C Fall 2013 -- Lecture 101 PHY 113 C General Physics I 11 AM – 12:15 PM MWF Olin 101 Plan for Lecture 10 Chapter 9 -- Linear momentum 1.Impulse and momentum 2.Conservation of linear momentum 3.Examples – collision analysis 4.Notion of center of mass

2. 10/01/2013 PHY 113 C Fall 2013 -- Lecture 102

3. 10/01/2013PHY 113 C Fall 2013 -- Lecture 103 Summary of physics “laws”

4. 10/01/2013PHY 113 C Fall 2013 -- Lecture 104 Another way to look at Newton’s second law: iclicker question: Why would you want to define linear momentum? A.To impress your friends. B.To exercise your brain. C.It might be helpful. D.To distinguish it from angular momentum.

5. 10/01/2013PHY 113 C Fall 2013 -- Lecture 105 Relationship between Newton’s second law and linear momentum: (if m is constant)

6. 10/01/2013PHY 113 C Fall 2013 -- Lecture 106

7. 10/01/2013PHY 113 C Fall 2013 -- Lecture 107 Suppose that a tennis ball with mass m=0.057 kg approaches a tennis racket at a speed of 45m/s. What is the impulse the racket must exert on the ball to return the ball in the opposite direction at the same speed. Assume that the motion is completely horizontal.

8. 10/01/2013PHY 113 C Fall 2013 -- Lecture 108 Example: A 1500 kg car collides with a wall, with v i = -15m/s and v f =2.6m/s. What is the impulse exerted on the car?

9. 10/01/2013PHY 113 C Fall 2013 -- Lecture 109 Example of graphical representation of F(t)

10. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1010 Physics of composite systems

11. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1011 Example – completely inelastic collision; balls moving on a frictionless surface

12. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1012 Energy loss in this example:

13. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1013 Example – completely elastic collision; balls moving on a frictionless surface

14. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1014 Completely elastic collision; numerical example:

15. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1015 iclicker exercise: We have assumed that there is no net force acting on the system. What happens if there are interaction forces between the particles? A.Analysis still applies B.Analysis must be modified

16. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1016 Example from homework:

17. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1017 Example from homework: -- continued iclicker question Do you expect K f -K i to be A.>0 B.<0

18. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1018 Another example: before vfvf after

19. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1019 Examples of two-dimensional collision; balls moving on a frictionless surface

20. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1020 Examples of two-dimensional collision; balls moving on a frictionless surface

21. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1021 Example: two-dimensional totally inelastic collision m 1 =1500kg m 2 =2500kg

22. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1022 iclicker exercise: Can this analysis be used to analyze a real collision? A.Of course! The laws of physics must be obeyed. B.Of course NOT! In physics class we only deal with idealized situations which never happen.

23. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1023 Another example of 2-dimensional elastic collision: m vivi vfvf m

24. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1024 Energy analysis of a simple nuclear reaction : Q=4.87 MeV

25. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1025 Energy analysis of a simple reaction : Q=4.87 MeV

26. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1026 Elastic collision in two dimensions

27. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1027 Elastic collision in two dimensions -- example of elastic proton-proton scattering

28. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1028 Elastic collision in two dimensions -- example of elastic proton-proton scattering

29. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1029 The notion of the center of mass and the physics of composite systems

30. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1030

31. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1031 Finding the center of mass

32. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1032 Example from webassign : x y m1m1 m2m2 m3m3 m4m4

33. 10/01/2013PHY 113 C Fall 2013 -- Lecture 1033 Finding the center of mass For a solid object composed of constant density material, the center of mass is located at the center of the object.