Unit
Test A
Name
Date
Work, Power, and Efficiency
Circle the best answer for each question.
1. Cheng uses a force of 25 kg to lift the handles of a
wheelbarrow. The total load of the wheelbarrow is 100 kg. What
is the mechanical advantage of the wheelbarrow?
A. 0.25
B. 1
C. 2
D. 4
2. Study the picture of a person moving a box up a ramp.
100
N
1 Meter
If she pushes with a force of 100 N, how much work has she
done by the time she reaches the top?
A. 1 J
B. 50 J
C. 100 J
D. 1,000 J
© McGraw-Hill Education
3. Melinda uses a pulley to raise a flag up the flagpole. Which will
increase the efficiency of the pulley?
A. attach a small weight to the flag
B. add oil to lubricate the pulley
C. use a longer rope
D. use a rope that weighs less
100
Unit 6 • Work, Power, and Efficiency
Use with Unit 6
Name
Unit
Test A
Date
4. How much more power will be needed to run up a flight of
stairs in one second compared to walking up the stairs in ten
seconds?
A. It would take one-tenth the power to run up the stairs.
B. It would take 100 times as much power to run up the stairs.
C. It would take 10 times as much power to run up the stairs.
D. It would take the same amount of power to run up the stairs.
5. A science student demonstrates the mechanical advantage of
two ramps. He uses a spring scale to measure the force
needed to pull a cart up each ramp. On ramp A, the reading on
the spring scale is 1 N. On ramp B, the reading on the spring
scale is 2 N. What can you infer about the ramps?
A. Ramp A is shorter and steeper.
B. Both ramps have the same mechanical advantage.
C. Ramp A has a higher mechanical advantage.
D. Ramp B has a higher mechanical advantage.
6. A student uses the same amount of force to push two boxes
across a floor. However, one box moves much farther than the
other. What can you infer from this information?
A. The boxes were pushed on different surfaces.
B. The two boxes have the same mass.
© McGraw-Hill Education
C. The same amount of power was used to push both boxes.
D. The student did more work to push the box that went farther.
Unit 6 • Work, Power, and Efficiency
Use with Unit 6
101
Unit
Test A
Name
Date
7. Susana uses the device below to pull a book across a table.
She will also measure the distance the book moved.
What is Susana most likely calculating?
A. power
B. work
C. mechanical advantage
D. efficiency
8. An electric motor uses 100,000 J to lift an elevator. Ms. Marion’s
science class calculates that it performs 90,000 J of work. What
is the efficiency of the motor?
A. 10 percent
B. 50 percent
C. 90 percent
© McGraw-Hill Education
D. 100 percent
9. Which is not an example of work?
A. pushing a shopping cart down an aisle
B. lifting books onto a shelf
C. pushing a door open
D. holding groceries
102
Unit 6 • Work, Power, and Efficiency
Use with Unit 6
Name
Unit
Test A
Date
10. Leonard attached a spring scale to a wood block and pulled it
over a concrete sidewalk and over a wood plank. Next he
poured water on the sidewalk and pulled the block over the wet
concrete. The readings on the spring scale were 6 N on the dry
concrete, 3 N on the wood plank, and 2 N on the wet concrete.
Which can Leonard conclude from his observations?
A. The wood had more friction than the dry concrete.
B. The dry concrete had less friction than the wood.
C. The wet concrete had more friction than the dry concrete.
D. The wet concrete had less friction than the wood.
11. What do these simple machines have in common?
Pulley
Inclined Plane
Lever
A. They all make it easier to do work.
B. They all have many parts.
C. They all work without any friction.
© McGraw-Hill Education
D. They all allow you to do less work.
12. The efficiency of a machine is never exactly 100 percent
because some energy is always lost due to
A. friction.
B. potential energy.
C. static energy.
D. deceleration.
Unit 6 • Work, Power, and Efficiency
Use with Unit 6
103