Classical Mechanics Friction: Examples Work &Kinetic Energy

1. Midterm 2 will be held on November 8. Covers units 4-9 Classical Mechanics Friction: ExamplesWork &Kinetic Energy JFB Rotunda David Matthew Stephens Lei Shan (Mike)

2. Schedule

3. Schedule

4. Schedule

5. Coupled Blocks with Friction A block (m2)slides on a table pulled by a string attached to a mass (m1)hanging over the side. The coefficient of kinetic friction between the sliding block and the table is mk. What is the tension in the string? m2 g m1

6. Tension in String • A block (m2) slides on a table pulled by a string attached to a mass (m1) hanging over the side. The coefficient of kinetic friction between the sliding block and the table is mk. What is the tension in the string? T1 T2 m2 g What is the relationship between the magnitude of the tension of the string at block 2 and the magnitude of the tension in the string at block 1? A) T1 > T2B)T1 = T2 C) T1 < T2 m1

7. Acceleration of coupled blocks A block (m2) slides on a table pulled by a string attached to a mass (m1) hanging over the side. The coefficient of kinetic friction between the sliding block and the table is mk. What is the tension in the string? m2 g m1 What is the relationship between the magnitudes of the acceleration of the two blocks? A) a1 = a2B) a1 < a2 C) a1 > a2

8. m2 1) FBD N T m2 g f T m1 m1 m2g m1g

9. m2 1) FBD 2) SF=ma N T m2 g f T m1 m1 m2g N = m2g m1g m1g – T = m1a T – mm2g = m2a add m1g – mm2g = m1a + m2a m1g – mm2g a = m1 + m2

10. m2 1) FBD 2) SF=ma N T m2 g f T m1 m1 m2g m1g m1g – T = m1a m1g – mm2g T = m1g – m1a a = m1 + m2 T is smaller when a is bigger

11. Accelerating Blocks

12. Accelerating Blocks

13. Carnival Ride

14. Carnival Ride

15. Accelerating Truck

16. Accelerating Truck

17. Mass on Incline

18. Mass on Incline

19. Mass on Incline

20. Mass on Incline 2

21. Mass on Incline 2

22. Mass on Incline 2

23. Mass on Incline 2

24. Block

25. Pushing Blocks

26. Midterm 2 will be held on November 8. Covers units 4-9 Classical Mechanics Lecture 7 Today’s Concepts: Work & Kinetic Energy JFB Rotunda David Matthew Stephens Lei Shan (Mike)

27. Lecture Thoughts

28. Kinetic Energy and Work

29. Work-Kinetic Energy Theorem The work done by force F as it acts on an object that moves between positions r1 andr2is equal to the change in the object’s kinetic energy:

31. What about Potential Energy??….next Unit!

32. Work-Kinetic Energy Theorem But again…!!! The work done by force F as it acts on an object that moves between positions r1 andr2is equal to the change in the object’s kinetic energy:

34. Newton’s 2nd law Work & Kinetic Energy

37. Vector Multiplication

38. The Dot Product

39. The Dot Product

40. The Dot Product

41. Work –Kinetic Energy Theorem: Work on sliding box Forces that act perpendicular to displacement perform no work!!!

42. Work –Kinetic Energy Theorem

43. Work done by Weight

44. Work –Kinetic Energy Theorem Applied

46. Work done by a Spring

47. Main Points

48. Main Points

49. Main Points