2. Work, Power and Simple Machines

3. Work Distance 10 m Force 40 N W = F * d = 40 N * 10 m = 400 Joules Force acting through a distance

4. Work l Force must be in same direction as distance Force Distance

5. Work l Force must be in same direction as distance Force Distance There is no work being done on the farmer

6. Power How fast (or the rate) Work is done P = W/t 400 J/1 sec = 400 watts 400 J/5 sec = 80 watts

8. How do machines make work easier? Work InWork Out DistanceForce DistanceForce DistanceForce DistanceForce Increase F MA>1 Increase D MA<1 Change direction of F MA=1

9. Even though machines make work easier, they cannot change the amount of work Work InputWork Output F effort *distanceF resistance *distance Work Input is always greater than Work Output due to Friction

10. Even though machines make work easier, % Efficiency = Work Output / Work Input *100 Work InputWork Output F effort *distanceF resistance *distance Work Input is always greater than Work Output due to Friction 10N*5m= 50J 20N*2m= 40J

11. Even though machines make work easier, % Efficiency = (40 J / 50 J) = 0.8 Work InputWork Output F effort *distanceF resistance *distance Work Input is always greater than Work Output due to Friction 10N*5m= 50J 20N*2m= 40J

12. Even though machines make work easier, % Efficiency = (40 J / 50 J) = 0.8 *100 =80% Work InputWork Output F effort *distanceF resistance *distance Work Input is always greater than Work Output due to Friction 10N*5m= 50J 20N*2m= 40J

13. Inclined Plane A slanted surface used to raise an object

14. Inclined Plane

15. 5 N

16. Inclined Plane l Decreases the size of the effort force 5 N 4 N

17. Inclined Plane l Decreases the size of the effort force 5 N 4 N

18. Inclined Plane l Decreases the size of the effort force l Increases the distance 5 N 4 N

19. Wedge An inclined plane that moves

20. Wedge An inclined plane that moves

21. Wedge An inclined plane that moves

22. Wedge An inclined plane that moves

23. Wedge An inclined plane that moves

24. Wedge An inclined plane that moves

25. Wedge As a wedge moves through an object to be cut,

26. Wedge A small effort force

27. Wedge A small effort force Is able to overcome

28. Wedge A small effort force Is able to overcome A large resistance force

29. Wedge A small effort force Is able to overcome A large resistance force

30. Wedge How can the mechanical advantage be increased?

31. Wedge How can the mechanical advantage be increased? Reduce the effort force by decreasing the angle

32. Screw An inclined plane wrapped around a central bar or cylinder to form a spiral

33. How fast (or the rate) Work is done

34. 1st class Mechanical Advantage = resistance F / effort F = 2 N

35. 1st class Mechanical Advantage = resistance F / effort F = 2/2 = 1 2 N

36. 2nd class Mechanical Advantage = resistance F / effort F = 2 N 1 N

37. 2nd class Mechanical Advantage = resistance F / effort F = 2/1 = 2 2 N 1 N

38. 3rd class Mechanical Advantage = resistance F / effort F 2 N 3 N

39. 3rd class Mechanical Advantage = resistance F / effort F = 2/3 = 0.66 2 N 3 N

41. 5 N Pulleys Fixed Movable

42. 5 N Pulleys 5 N 2.5 N Fixed Movable MA = 5/5=1 MA = 5/2.5 =2

43. 5 N Pulleys 5 N 2.5 N Resistance distance = Effort distance Resistance distance = 1/2 Effort distance

44. Wheel and Axle l Two circular objects of different size l The wheel always moves a greater distance than the axle

45. Wheel and Axle l Wheel : Large Distance, Small Force l Axle : Small Distance, Large Force

46. Compound Machine Corkscrew l Inclined Plane? l Wedge? l Screw? l Lever? l Pulley? l Wheel and Axle?

47. Compound Machine Corkscrew l Inclined Plane l Wedge l Screw l Lever l Pulley l Wheel and Axle

48. Compound Machine Drill l Inclined Plane? l Wedge? l Screw? l Lever? l Pulley? l Wheel and Axle?

49. Compound Machine Drill l Inclined Plane l Wedge l Screw l Lever l Pulley l Wheel and Axle

50. Compound Machine Jack l Inclined Plane? l Wedge? l Screw? l Lever? l Pulley? l Wheel and Axle?

51. Compound Machine Jack l Inclined Plane l Wedge l Screw l Lever l Pulley l Wheel and Axle