Next year show how balanced torque problems can be kept in g and cm more.

1. Next year show how balanced torque problems can be kept in g and cm more.

2. A Force causes an object to accelerate A Torque causes an object to rotate Torque Force

3. Anytime you rotate an object you apply a torque

4. When you open door, it rotates. Where is the pivot point / axis of rotation?

5. A B To open a heavy door where would you push on the door to make it easiest? C

6. The distance from the pivot point to the location of the force is called the LEVER ARM (distance) A B C The longer the lever arm the greater the torque

7. This force has no lever arm and produces no torque or rotation

8. The direction of the force matters too, how well will these two forces work for opening the door? B A

9. To Rotate an object the force must be applied perpendicular to the lever arm (the door in this case) B A A is perpendicular to the lever

10. TORQUE t = F d lever arm length (m) NOT distance traveled Force perpendicular to lever arm (N)

11. The greater the torque the faster an object will rotate or turn

12. Torque MORE Torque Where should you hold the wrench in order to loosen a stubborn bolt? t = F d Force Force

13. A wrench is all about TORQUE You create the most torque by holding the wrench at the end and by exerting a large force. If you can’t loosen the bolt with all your strength, what do you do?

14. Force Force Get a longer wrench!! lever arm Even with the same force, twice the lever arm gives twice the TORQUE

15. The greater the force,the greater the torque t = F d Force Torque Force MORE Torque

16. only the blue part counts The more perpendicular the force the greater the torque t = F d Force Torque Force MORE Torque

17. Any force which points through the axis of rotation creates no torque Force t = F d Torque = 0

18. What is the torque generated by pushing With a force of 5.0 N on a wrench which is 20 cm long?

19. Torque requirement on your tires lug nuts is 190 Nm. If you have a wrench which is .25 m, how hard do you have to push? .25 m

20. Consider the two wrenches below, compare torques If the applied force is the same F F

21. F The lever arm distance is really still the same F

22. Another way of looking at torque, this is easier in some situtations. 3.) The lever arm is the distance that line to the center of rotation lever arm distance 1.) Draw a line through the force 2.) Bring a line perpendicular to the previous line through the axis of rotation 4.) Torque = Total force x lever arm

23. 1.) Draw a line through the force 2.) The lever arm is the distance that line to the center of rotation 3.) Torque = Total force x lever arm Lever arm distance (d) F

24. 1.) Draw a line through the force 2.) The lever arm is the distance that line to the center of rotation 3.) Torque = Total force x lever arm Lever arm distance (d) F

25. A force of 100 N is exerted as below on a rope attached to a .25 m wrench. What torque is generated? 100 N .2 m

26. F

27. TORQUE is also a vector. We will just think of torque as CW or CCW CCW CW

28. Two 400 N children balance on a seesaw The same force on each side, right 400 N 400 N 1 m 1 m

29. 400 N What if one child scoots in? Forces are still equal on both sides 400 N 1 m 0.5 m

30. 400 N BUT THE TORQUES DO NOT 400 N 1 m 0.5 m t = 400 Nm (CCW) t = 200 Nm (CW) Nett = 200 Nm (CCW)

31. To prevent an object from rotating there can be no net TORQUE OR tcw = tccw

32. If there is no net torque then an object does not…. Rotate (its rotation speed does not change is the more accurate statement) If there is no net force then an object does not…. Accelerate

33. 100 N Can a big kid and a little kid balance on a seesaw? 400 N

34. 100 N The bigger kid must move closer the to fulcrum to lower his torque 400 N ? 1 m 0.25 m What is the upward force at the pivot point?

35. ? N If the seesaw balances what is the weight of the other person? 400 N 1 m .75 m

36. 200 N d 2d If a 400 N person and a 200 N person want to balance where should be fulcrum be placed? 400 N So that the lever arm is twice as much for the 200N person or 2/3 away from them

37. 100 N d 5d If a 500 N person and a 100 N person want to balance on the ends of a 3 m seesaw where should be fulcrum be placed? 500 N So that the lever arm is 5 x as much for the 100N person or 5/6 away from them

38. Correct this statement: An object balances when the same weight is on both sides of the pivot point An object balances the weight on either side of the pivot point create equal torques

39. A mass on a string exerts a torque on a pulley, what is lever arm & direction of torque

40. DEMONSTRATION: Will the object rotate .25 m .10 m 500 g 500 g

41. Torque WS

42. Torque lab

43. Torque Feeler Demo

44. What causes an object to change its rotational speed? How do you create torque? When does a force create NO torque?

45. Which force creates more torque? NEITHER creates any TORQUE, since they both point to the axis of rotation

46. Demo – balanced / unbalanced meterstick is there a net torque?

47. FN = mg Fg = mg Is there a net force? Is there a net torque?

48. FN Fg If the CM isn’t under a pivot gravity creates torque. What is the lever arm? What is the axis of rotation? Does the normal force from the pivot create torque? Is there a net force? Is there a net torque?

49. A 6 meter long board has a weight of 800 N. If a fulcrum is placed under it 2 m from one end, what is the torque on it.

50. What torque does gravity create on a .35 kg meterstick which is supported at the 15 cm mark? Fg