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Machines and Work Notes
Working Hard or Hardly Working?
1. Work is done when a __________ causes an object to move in the __________ direction as the
force.
2. Applying a force doesn’t always result in _________ being done.
3. Work is done on an object if __________ things occur:
a. The object __________ as a force is applied.
b. The __________ of the objects motion is the __________ as the direction of the force applied.
Force and Motion
4. If the object does __________ move, then __________ work is done.
5. If the object __________ in the direction of the applied force, then person does __________ on
object.
Force and Direction
6. ↑ = direction of force on object; → = motion of object. Is work done? Why or why not?
7. → = direction of force on object; → = motion of object. Is work done? Why or why not?
8. Your neighbor asks you to help push his stalled car. You push and push but the car doesn’t move.
You are exhausted and sweaty. Have you done any work? Explain your answer.
Calculating Work
9. The equation for calculating work is: Work
10. The unit for force = _______________
11. The unit for distance = _______________
12. The unit for work = __________
= Force x _______________
Work
13. Work __________ is the work you do on a machine.
14. You apply a force, called the __________ __________, to the machine to move it through a
distance.
15. Work __________ is the work done by the machine.
16. The machine applies a force, called the __________ __________, through a distance.
17.
Work output can __________ be greater than work
input.
18.
If you want to get to point C on the illustration below
you have two options:
Start at A and go straight up, or start at B and walk up the slope.
Which requires less work?
Making Work Easier
19. Machines are __________ that make work __________.
20. Machines can change the amount of _______________ you exert.
21. Machines can change the _______________ over which you exert force.
22. Machines can change the _______________ in which you exert force.
23. Machines do __________ change the amount of work done!
Force-Distance Trade-off
24. When a machine changes the __________ of the force, the _______________ through which the
force is exerted must also change.
25. Force _____ distance can increase, but _____ together.
26. When one increases, the other must _______________.
27. The work output is __________ greater than the work input.
Total Work Does Not Change
Work = _______________ x Distance
28. If a machine allows you to apply a smaller force the distance will _______________.
Draw an example.
29. If a machine allows you to move a shorter distance the effort _______________.
Draw an example.
30. If a machine allows you to apply a force in a different _______________ it might not change how
much force you have to apply or how far you move it.
Draw an example.
Mechanical Advantage
31. A machine’s mechanical advantage tells you how many times the machine _______________
force.
32. Mechanical Advantage = MA =
33. You apply 200 N to a machine and the machine applies 2,000 N to an object.
What is the MA?
34. Which of the following machines has a greater mechanical advantage?
A. Input force = 50 N and output force = 150 N
B. Input force = 60 N and output force = 200 N
C. Force applied to machine = 25 N and machine applies a force of 100 N
D. Force applied to machine = 40 N and machine applies a force of 125
Types of Simple Machines:
Lever:
35. A board or bar that __________ at a fixed point
36. _______________ = pivot point
37. 3 classes of levers based on locations of ____________, the load, and the input __________.
38. Fill in the chart:
Type of Lever
Drawing
Examples
Advantage in using
st
1 class
2nd class
3rd class
Pulley:
39. A grooved _______________ that holds a rope, chain, or wire.
40. A __________ is attached to one end of the rope; an __________ __________ is applied to the
other end.
41. There are _____ kinds of pulleys: fixed and movable.
42. Examples of pulleys:
43. Fixed Pulley:
a. Pulley doesn’t __________ when the rope is pulled
b. You pull __________ to lift the load
c. Sketch a fixed pulley in the box.
44. Moveable Pulley:
a. Pulley __________.
b. Weight is attached to moveable pulley.
c. As the rope is pulled __________, the pulley and weight move up.
d. Sketch a moveable pulley in the box.
Inclined Plane:
45. A __________ surface used to raise or lower things; a __________; Does __________ move
46. Inclined planes allow you to apply a _______________ force over a greater _______________.
47. Mechanical Advantage of an inclined plane =
48. Examples of inclined planes:
49. What is the mechanical advantage of an inclined plane 3 m long and .5 m high?
50. A winding road is actually a series of inclined planes. Describe how a winding road makes it easier
for vehicle to travel uphill.
51. Why would you not want to reduce the friction involved in using a winding road?
Wedge:
52. Two inclined planes back to back
53. A wedge ___________.
54. Holds things together or __________ things apart
55. Mechanical Advantage of a wedge =
56. Examples of wedges:
57. Which knife gives you a better mechanical advantage:
a. A short and fat knife
b. A short and thin knife
c. A long and fat knife
d. A long and thin knife
Screw:
58. An inclined plane _______________ in a spiral
59. When rotated a small ___________ is applied over the long __________ along the inclined plane of
the screw
60. Most commonly used as _______________; examples:
Wheel and Axle:
61. Two _______________ objects of different sizes; One is a __________, one is an axle.
62. As the wheel turns, so does the __________.
63. Mechanical Advantage of a wheel and axle: =
64. What is the mechanical advantage of a wheel and axle where the wheel’s radius is 10 cm and the
axle’s radius is 2 cm?
Compound Machines
65. Compound machines are made of two or more _______________ machines.
66. List the simple machines found in these common compound machines.
Compound Machine
Types of simple machines that make it up:
Stapler
Can opener
Pencil sharpener
Bicycle
67. How are simple machines an important part of your life? Give examples written in at least two
COMPLETE sentences.