1. Who can lift me with 1 hand?

2. Simple machines help make a job easier by:
Changing how much FORCE is NEEDED
or the Direction of the Force
Archimedes once said: give me a lever long enough and a
place to stand and I will move the earth

3. Machines are all just combinations of 4 basic type:
Lever
Pulley
Wheel & Axle
Inclined Plane

4. The force you apply to the machine
Effort Force, FE
The force you apply to the machine FR FE
Resistance Force, FR :
The force actually applied to the resistance
(usually equal to the weight of an object)

5. Distance of effort (dE)
By pushing on the lever you do WORK on it FE FR
Distance of effort (dE)
Work input = FEdE

6. Distance of resistance (dR)
AND WORK COMES OUT
Distance of resistance (dR) FE FR
Work Ouput = FRdR

7. FRdR = FEdE FR dE if an ideal machine work out = work in
Compare the Work Out to the work input
FRdR = FEdE
work out = work in
The lever used to lift me reduced the Force needed to lift me but not the WORK!!! FR FE dE dR
if an ideal machine

8. Work Output = Work Input
If no energy (or work) is lost to friction then….
Work out FE FR
Work in
Work Output = Work Input

9. Work Output = Work Input
(For an ideal machine – no friction)
This is a best case &
You can never get more work out
than the work put in!!!!
That would be like making energy

10. Simple machines magnify the input force but at a cost….

11. FR MA = FE FR FE Mechanical Advantage
This is how much your force gets multiplied by a machine, or
by how much the required force to do a job is reduced
If MA >1 then…
If MA < 1 then…

12. What’s is the MA?
10 N
100 N

13. What’s is the MA?
200 N
100 N

14. Is the lever ideal (frictionless)?
The effort side of a lever is pushed down with a force of 90 N for 1.8 m. This lifted a box weighing 270 N up .6 m.
What is the work input?
What is the work output?
What is the MA?
Is the lever ideal (frictionless)? FE FR

15. One side of a lever is pushed down by a person with a force of 50 N and a 200 N object is lifted. If the person pushes the lever down 1 m, how far does the other side move up? (if the lever is frictionless) FE FR

16. If an ideal lever is such that when a person pushes their side down
If an ideal lever is such that when a person pushes their side down .8 m, it lifts a load on the other side up .2 m. If the load weighs 100 N, how hard does the person need to push? FE FR

17. If there is no friction then the Mechanical Advantage
can be determined by looking at the distances
What is the ideal Mechanical Advantage here?
6 m
2 m

18. IDEAL MECHANICAL ADVANTAGE
Because we ratio of the distances is related to how much the Effort Force gets magnified.
IDEAL MECHANICAL ADVANTAGE dE
IMA = dR
This is the MA if there is no friction

19. What is the IMA?
.75 m
.25 m

20. Where should the fulcrum (pivot point) be placed to reduce the applied force?

21. What happens it the fulcrum is placed in the middle?

22. 500 N
100 N
What happens to the applied force if the fulcrum is moved closer to it?

23. Book Problems
Read pages
Page , 15,16,17, 18,19
28 –Find the MA, IMA TOO
29 – only part a.)

24. Type 1
TYPES OF LEVERS
Resistance
Effort
The difference is the relative locations of the effort, fulcrum, and resistance
Type 2
Resistance
Effort
Type 3
Effort

25. How does the direction of applied force vary?
Type 1
TYPES OF LEVERS
Resistance
Effort
Type 2
How does the direction of applied force vary?
Resistance
Effort
Type 3
Effort
Resistance

26. Compared to the resistance can each type make the applied force
Effort
Compared to the resistance can each type make the applied force
Less, more, or both?
Type 2
Resistance
Effort
Type 3
Effort
Resistance

27. Type 1 Type 2 Type 3 Resistance Effort Resistance Effort Effort

28. Which type of lever is this?
input
output

29. Which type of lever is this?
input
output

30. ID the levers
input
output

31. ID the levers
output
input

32. Pulleys
They range from simple
To complex

33. Simple Pulley is just a round wheel with an axle in the middle and a groove to keep a rope on it

34. A Simple Pulley Direction of Forces Which moves more? Output force
Input force
100 N

35. What is the MA of this type of machine?
The force and resistance must move the same amount so the FE = FR

36. A pulley like this acts like a Type 1 Lever with the fulcrum in the middle
Forces are reversed
with equal magnitudes
100 N
100 N
100 N

37. Will the input Force be 100 N?
Output force
100 N

38. The Effort force is ½ the Resistance

39. To lift the resistance 1 m
2 m of rope must be pulled
1 m

40. What is the MA of this type of machine?

41. Typically the number of strings attached to the load is the MA

42. A pulley like this acts like a Type 2 lever with the resistance in the middle

43. Pulleys can be combined to change direction and magnify the effort force

44. But what is the tradeoff here? The Possibilities are Endless!

45. Simple machines WS

46. Simple machines lab

47. Go over simple machines ws

48. ID the levers

49. How much your force is multipliedFR
How much your force is multiplied
MA = FE
If an IDEAL pulley has an MA of 4, how much rope do you need to pull to lift the resistance 2 m?
4 times as much or 8 m

50. NO work or energy is “lost” as
For an IDEAL Machine
WorkOUT = WorkIN
HEAT
NO work or energy is “lost” as
If there is no FRICTION

51. Input work output work heat
Realistically there is always some friction
10 J
8 J
Input work
output work
2 J
heat
So in the real world you never get out as useful work what you put in

52. Efficiency is what % of the input work comes out at useful work
Work out
100%
Efficiency =
Work in

53. If a machine is 50% efficient
Work out
50 J
50 % =
100 J
Work in
You have to put 100 J of work in to get 50 J out

54. For an ideal machine Work Output = Work Input
If a 100 J is put in then 100 J comes out
100 J
Efficiency =
100 J
Efficiency = 100%

55. A frictionless lever belowFE FR dR dE
Work in = Work out
Efficiency = 100%

56. To overcome friction extra force must be applied to do the same thingFE FR dR dE

57. A lever is such that if the effort side is pushed down 2 m with a force of 3 N, a 4 N load is lifted 1 m. What is the efficiency of the lever?

58. Using a machine which is 20% efficient, how much work will have to be applied to a machine to lift a 10 N weight up 2 m?

59. To overcome friction extra force must be applied to do the same thingFE FR dR dE

60. FE What changed because of friction FR FE dE dR
To overcome friction extra force must be applied to do the same thing FE FR dR dE
What changed because of friction FE FR FE dE dR

61. FE FE How does that affect FR MA = FR FE dE dR
To overcome friction extra force must be applied to do the same thing FE FR dR dE
How does that affect FR MA
MA = FE FE FR FE dE dR

62. FE How does that affect dE IMA = dR FR FE dE dR NO CHANGE
To overcome friction extra force must be applied to do the same thing FE FR dR dE
How does that affect dE
IMA = FE dR FR FE dE dR
NO CHANGE

63. FE Work in How does that affect Work in = FE dE FR FE dE dR
To overcome friction extra force must be applied to do the same thing FE FR dR dE
How does that affect
Work in = FE dE FE
Work in FR FE dE dR

64. FE How does that affect Work out = FR dR FR FE dE dR NO CHANGE
To overcome friction extra force must be applied to do the same thing FE FR dR dE
How does that affect FE
Work out = FR dR FR FE dE dR
NO CHANGE
Work out

65. FE Work in How does that affect FR FE dE dR Work out Efficiency =
To overcome friction extra force must be applied to do the same thing FE FR dR dE
How does that affect FE FR FE dE dR
Work out
Efficiency
Efficiency =
Work in

66. SHOW WORK WHERE APPLICABLE
Book Problems
Page 120:, 29 b, 39, 42, 43, 45, 47
X.) How much input work will be needed to do 300 J of output work using a machine which is 35% efficient? How much work is lost as heat?
Q.) In lifting a 1.5 kg mass up 2.0 m, the effort side of a lever is pushed down with 10.0 N of force for 4.0 m. What is the efficiency of the lever?