1. Machine – device that makes work easier

2. B. Work – when an object moves in the same direction as the force applied

3. Unit: Joule (J) or NewtonMeter (Nm)
Work = Force x Distance
Unit: Joule (J) or NewtonMeter (Nm)

4. Using a ramp (simple machine) makes it easier for April to move the speaker onto the stage.4

8. C. Power – measures how fast you can do work
Power = Work / Time
Unit: Watt (W)

9. When April lifts a trumpet or a tuba up the stairs, she does work.9

10. Power equals the amount of work done on an object in a unit of time
Power equals the amount of work done on an object in a unit of time. How much time would it take April to move her boxes upstairs if she runs? 10

11. D. How does a machine make work easier?
1) They change the amount of the force applied.
2) They change the direction of the force applied.

12. E. Mechanical Advantage
Measures how much easier a machine makes work

13. 1) Input (Effort) Force:
Force exerted by a person on the machine.

14. 2) Output (Resistance) Force
Force exerted by the machine on the object.

15. 3) Draw the pulley below.
Input force
Output Force

16. 4) Mechanical Advantage =
Output Force
_________________
Input Force

17. 17

18. Drums are tuned by tightening and loosening bolts
Drums are tuned by tightening and loosening bolts. Drum keys make the bolts easier to turn. 18

19. Which one would be best to play seesaw?

22. Ideal Machine = 100% efficient
Efficiency: measures how effective a machine is Work output x 100 Work input
Ideal Machine = 100% efficient
** meaning you get out what you put in**

23. Ideal machines (100% efficient) do NOT exist !
Because all machines waste some work overcoming friction

25. Simple Machine
Simple Machine: a device that does work with only one movement.

26. Using a machine does not mean that you do less work, they make the work easier to do.

27. Simple Machines (6 types)
Lever, pulley, wheel and axis, inclined plane, screw, wedge

28. Inclined plane (ramp)- a flat surface that slopes upward

30. Inclined Plane
M.A. = length of slope
Height 30

32. Calculate the mechanical advantage.

33. Calculate the mechanical advantage.

35. Which has higher M.A.?

36. Wedge – a triangular, V-shaped object

38. Wedge
M.A. = Length of Wedge
Width of Wedge 38

39. Screw- inclined plane wrapped around a post

40. Screw
The threads of a screw act like an inclined plane to increase the distance over which input force is exerted. 40

41. Levers – a bar that pivots at a fixed point

42. Levers Mechanical Advantage
M.A. = Length of effort arm (Input arm) Length of resistance arm (Output arm)

45. Which one gives you a greater M.A.?
Levers
Which one gives you a greater M.A.? 45

46. Levers in the Body
Levers can be found throughout your body. In the last two panels of the diagram, where would the output force be? What is the class of lever for each part of the body? 46

47. Levers have the following:
Fulcrum – fixed pivot point
Effort arm – force is applied here
Resistance arm – exerts the force from the effort arm

48. Pulley – a rope or chain that wraps around a wheel

49. M.A. = number of sections of rope that support the object
Pulleys
M.A. = number of sections of rope that support the object 49

50. 1) What type of pulley is this? 2) What is the M.A. of this system?

51. Wheel and axle – a large wheel turns a smaller axle

52. Wheel and Axle
M.A. = radius wheel
radius axle
10 cm
2 cm 52

53. Which one has a higher M.A.?

54. Simple Machines in Sailboats
You can find many simple machines on a sailboat. Where are the pulleys on the diagrams? 54

56. Simple Machines
You cannot get more work from a machine than you put into it.
Machines simply decrease your effort and make the work easier.
Simple Machines all do work the same way: by moving an object through a distance.

57. 5) The higher the mechanical advantage, the Less the effort force is and therefore the better the machine is.

58. Compound Machine: two or more simple machines working together

59. 6) M.A. = resistance force / effort force
= 6 / 2
= 3

60. Frivolous machines

63. Work – transfer of energy through motion

64. 2 conditions for work to be done
Force must be applied
Object must move in direction of the force

65. Equations for Work: W = F x d Unit for Work = Joule (J)
Work = force x distance
W = F x d
Unit for Work = Joule (J)

66. Practice problem W = F x d W = 2400 Nm or J d = 30 m F = 80 N W= ?
You move a stove a distance of 30 meters. This requires a force of 80 N. How much work did you do?
W = F x d
d = 30 m F = 80 N W= ?
= 80 N x 30 m
W = 2400 Nm or J