1. Simple Machines Mechanical Advantage WORK 1 Efficiency Effort Force
Sound
Efficiency
Effort
Mechanical Advantage
WORK
Force

2. 2
Goals
What do I need to know?
1.Analyze the simple machines qualitatively and quantitatively in terms of force, distance, work and mechanical advantage
2. Explain the different types of simple machines.
3. Be able to calculate amount of work done by a simple machine
4.Be able to calculate mechanical advantage
5. Use mathematics & computational thinking to identify the relationships between work, mechanical advantage, and simple machines

3. Working Together

4. Work FLASH BACK Transfer of Energy from one place to another.3
Work
FLASH BACK
Transfer of Energy from one place to another.
Applying a force over a certain distance.
Calculating Work:
Work= Force x distance
W = f x d

5. 6 types of simple machines4
6 types of simple machines
clip

6. What is a machine? -a machine that does work with only one movement.5
A device that makes work easier.
What is a simple machine?
-a machine that does work with only one movement.
You still do the same amt of work —it’s just easier!

7. A machine can make work easier in two ways:6
A machine can make work easier in two ways:
Multiply the force you apply.
A Car Jack
Change the direction
of the force.
Blinds

8. 7.1
Mechanical Advantage
CLIP
Number of times the machine multiplies the effort force
(The force you apply to it)

9. Ideal vs Actual Mechanical Advantage
7.1
Ideal vs Actual Mechanical Advantage
IMA- The mechanical advantage of a
machine in the absence of friction
WHAT ACTUALLY happened!!
Why is this different from IMA?
AMA- The mechanical advantage of a
machine in the presence of friction

10. Watch for this in all Simple machines:8
Watch for this in all Simple machines:
Machines are a “give and take relationship.” If you get your force multiplied, then you must go a greater distance.

11. Efficiency of a Machine9
A measure (%) of how much work put into a machine is actually changed to useful work put out by the machine.
90 J .
100 J
NEVER OVER 100%

12. According To “The Law of Conservation of Energy” Can this exist?10
Ideal machine
Efficiency =100%
According To “The Law of Conservation of Energy” Can this exist?
Does not exist.
FRICTION

14. Types of Machines Levers11
Types of Machines Levers
A lever is a bar that is free to pivot, or turn about a fixed point.
How can we use levers?

15. Levers 12 Fulcrum Resistance Distance Effort Distance Effort Arm
LOAD
Effort Arm
Resistance Arm
Resistance Force
Effort Force

16. Levers There are three types of Levers13
Levers
There are three types of Levers
Based on the position of the fulcrum

17. The fulcrum is between the resistance force and the effort force.14
Levers
1st Class: Crowbars, pliers, scissors, seesaw
The fulcrum is between the resistance force and the effort force.
The closer the fulcrum to the resistance force, the more the lever multiplies the force.

18. Levers 15 Wheelbarrow Nutcrackers Crowbar (forcing two objects apart)
2nd Class: The resistance force is between the effort force and the fulcrum.
Wheelbarrow
Nutcrackers
Crowbar (forcing two objects apart)
The handle of a pair of nail clippers

19. 16
3rd Class: the effort force is between the resistance force and the fulcrum.
Levers
Garden Hoe
Your arm
Catapult
Fishing rod
Tongs (double lever) (where hinged at one end)

20. Mechanical Advantage of Levers17
Mechanical Advantage of Levers
3 Ways
5/5=1
10/5=2
20/5=4
Effort arm
Resistance arm
As the length of the effort arm increases, the MA of the lever increases.

21. Mechanical Advantage of Levers
You can also use the Mechanical Advantage Formulas:
IMA
Ideal MA
AMA
Actual MA

22. 18
REVIEW
Position of Fulcrum

23. MA of Levers Problems
To pull apart two pieces of wood, you apply a force of 50 N to a lever. The lever then applies a force of 640 N to the wood. What is the mechanical advantage of the lever?
A lever and fulcrum are used to raise a heavy rock, which has a weight of 350 N. If the lever has a mechanical advantage of 9, what must the input force on the lever be in order to just begin lifting the rock?
A construction worker uses a board and log as a lever to lift a heavy rock. If the input arm is 6 meters long and the output arm is 1.2 meters long, what is the mechanical advantage of the lever?

25. 19
Pulleys

26. Pulleys Multiply the effort force change the direction of the force 20
What is a pulley?
A pulley is a grooved wheel with a rope or chain running along the groove.
What can a pulley be used for?
Multiply the effort force
change the direction of the force

27. Pulleys 21 Two types of Pulleys: Fixed pulley Movable pulley
A pulley that is attached to
something
Only changes the direction of
the force
Movable pulley
The pulley is free to move
***Block and Tackle***
Combination of both types of pulleys

28. Mechanical Advantage of Pulleys22
Only changes the direction of the force
MA =1
10 N
resistance Force
Effort Force
10 N

29. Mechanical Advantage of Pulleys23
MA =2

30. Mechanical Advantage of Pulleys24
MA =2

31. Mechanical Advantage of Pulleys25
MA =4

32. 26

33. 27

34. 28
Inclined Plane
A sloping surface that that reduces the amount of force required to raise and object.
Resistance Distance (h)
Effort Distance (l)

35. Mechanical Advantage of Inclined Planes29
Effort Distance (l)
Resistance Distance (h)

36. Mechanical Advantage of Inclined Planes30

37. Animation Starter on page 6 in packet…click

38. 31.a
Wheel and Axle
Consisting of two wheels of different sizes that rotate together
The effort force is applied to the larger wheel

39. The effort force is applied to the larger wheel
31.b
Ideal Mechanical Advantage = Radius of wheel
    Of wheel and axle        Radius of axle
The effort force is applied to the larger wheel
Gears are wheels with teeth.

40. 31.c
One day you made a mousetrap cars The car has the following measurements for their wheels:  the radius axle (the small wheel) measured only 1 cm.  The radius of the larger wheel (the one that touched the pavement) measured a whopping 10cm.  What was the mechanical advantage of these wheels?
Ideal Mechanical Advantage = Radius of wheel
    Of wheel and axel        Radius of axel
IMA = 10
This means with each turn of the axle, you get 10 times the distance.  Those big wheels really help!

41. Screw An inclined plane wrapped around a cylinder32
Screw
An inclined plane wrapped around a cylinder
The inclined plane lets the screw slide into the wood.
Examples: Bolt, Spiral Staircase

42. 33

43. Wedge 34 An inclined plane with one or two sloping sides.
Changes the direction of the effort force.
Examples: Axe, Zipper, Knife
Effort Force
Resistance force

44. Review Clip 35

45. 36
Rube Goldburg
Keep You From Forgetting To Mail Your Wife's Letter

46. 37
Simplified Pencil Sharpener
CLIP

47. EOCT
QUESTIONS 38

48. A lever is used to lift a box. The mechanical advantage of the lever is39
It took only 200 N of force to lift a 1000N object, therefore the machine multiplied the force 5 times!
A 25 B 10 C 5 D 4 OR
50 cm
10 cm

49. 40
What is the amount of useful work output of a 25% efficient bicycle if the amount of work input is 88 N-m?
A 2200 N-m
B 113 N-m
C 63 N-m
D 22 N-m
Wout
.25 =
88 J

50. Which of the following is an example of41
Which of the following is an example of
a compound machine?
A bicycle
B crowbar
C doorknob
D ramp

51. Simple Machines