Georgia Science Grade 8

Chapter 14: Work and Simple Machines

CRCT Practice

1
A child does 450 J of work in pulling a snow sled up a hill in 10.0 s. What is the power the child uses?
A)24.7 W
B)45.0 W
C)4,500 W
D)0.2 W
2
What is the mechanical advantage of the lever?

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A)1/6
B)1/2
C)6
D)2
3
What would the mechanical advantage of the lever be if the triangular block were moved to a position 40 cm from the edge of the output force side of the plank?

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A)2.5
B)2
C)3
D)0.4
4
This pulley system uses several pulleys to increase the mechanical advantage. What is the mechanical advantage of this system?

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A)1
B)2
C)3
D)4
5
Suppose the lower pulley was removed so that the object was supported by only the upper pulley. What would be the mechanical advantage?

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A)0
B)1
C)2
D)3
6
What is the mechanical advantage of a wheel with a radius of 8.0 cm connected to an axle with a radius of 2.0 cm?
A)0.25
B)2.5
C)4.0
D)16
7
Which causes the efficiency of a machine to be less than 100 percent?
A)work
B)input force
C)output force
D)friction
8
You push a box a distance of 3.0 m by exerting a force of 30 N. How much work did you do?
A)10 J
B)90 J
C)0.10 J
D)30 J
9
What type of simple machine is the tip of the dart?

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A)lever
B)wedge
C)wheel and axle
D)screw
10
How much energy is used by a 75-W lightbulb in 10 s?
A)7.5 J
B)75 J
C)750 J
D)0.03 J
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