Question

Multiple Choice
Write the letter that best answers the question or completes the statement on
the line provided.
1. A force acting on an object does no work if
a. a machine is used to move the object.
b. the force is not in the direction of the object’s motion.
c. the force is greater than the force of friction.
d. the object accelerates.
2. If you exert a force of 10.0 N to lift a box a distance of 0.75
m, how much work do you do?
a. 0.075 J b. 7.5 J
c. 10.75 J d. 75 J
3. If you perform 30 joules of work lifting a 20-N box from the
floor to a shelf, how high is the shelf?
a. 0.5 m b. 0.6 m
c. 1.5 m d. 2 m
4. If you exert a force of 500 N to walk 4 m up a flight of stairs
in 4 s, how much power do you use?
a. 31 W b. 500 W
c. 2000 W d. 8000 W
5. Which of the following statements is true?
a. To increase power, you can decrease the amount of work
you do in a given amount of time, or you can do a given
amount of work in less time.
b. To increase power, you can decrease the amount of work
you do in a given amount of time, or you can do a given
amount of work in more time.
c. To increase power, you can increase the amount of work
you do in a given amount of time, or you can do a given
amount of work in less time.
d. To increase power, you can increase the amount of work
you do in a given amount of time, or you can do a given
amount of work in more time.
6. A 750-W motor might also be rated as a
a. 0.5-horsepower motor. b. 1-horsepower motor.
c. 2-horsepower motor. d. 10-horsepower motor.
7. When a machine does work, it can do all of the following
EXCEPT
a. change the direction of a force.
b. increase a force and change the distance a force moves.
c. increase the distance a force moves and change the
direction of a force.
d. increase a force and increase the distance a force moves.

Answer 1

1. b
2. b (W = Fd = 10.0 N × 0.75 m = 7.5 J)
3. c (h = W/F = 30 J / 20 N = 1.5 m)
4. b (Work = 500 N × 4 m = 2000 J; Power = 2000 J / 4 s = 500 W)
5. c
6. b (≈746 W = 1 hp)
7. d