Multiple Choice
Identify the
choice that best completes the statement or answers the question.
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1.
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A boy exerts an average force of 65 N when he lifts a box 1.2 meters. How much
work does he do?
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2.
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How much power is required to do 180 J of work in 2.4 s?
a. | 7.5 W | c. | 178 W | b. | 75 W | d. | 430 W |
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3.
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How much power is required to lift a 30.0 N chair 0.20 m in 2.0 s?
a. | 1.0 W | c. | 12 W | b. | 3.0 W | d. | 15 W |
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4.
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What is the mechanical advantage of a single, fixed pulley?
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5.
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Calculate the gravitational potential energy relative to the ground when an 82
kg person climbs to the top of a 2.0 m stepladder.
a. | 164 J | c. | 402 J | b. | 3.3 ´
102 J | d. | 1.6 ´ 103 J |
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6.
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What is the kinetic energy of a 1.40 kg discus with a speed of 22.5 m/s?
a. | 15.8 J | c. | 354 J | b. | 31.5 J | d. | 709 J |
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7.
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A dog running at a speed of 12 m/s has 1,080 J of kinetic energy. What is the
mass of the dog?
a. | 7.5 kg | c. | 30 kg | b. | 15 kg | d. | 45 kg |
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8.
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An astronaut with a mass of 91 kg is 0.30 m above the moon’s surface. The
astronaut’s potential energy is 46 J. Calculate the free-fall acceleration on the moon.
a. | 0.15 m/s2 | c. | 6.6 m/s2 | b. | 1.7 m/s2 | d. | 9.8
m/s2 |
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9.
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_____ is the ratio of useful work output to work input.
a. | Potential energy | c. | Kinetic energy | b. | Efficiency | d. | Power |
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10.
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How efficient is a machine that uses 130 J to lift a 50.0 N load 2.0 m?
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11.
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A boy pushes on a parked car with a force of 200 N. The car does not move. How
much work does the boy do on the car?
a. | 200 N | c. | zero | b. | 200 L | d. | None of the
above |
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12.
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What are the units of work?
a. | J | c. | kg • m2/s2 | b. | N • m | d. | All of the
above |
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13.
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A weightlifter presses a 400 N weight 0.5 m over his head in 2 seconds. What is
the power of the weightlifter?
a. | 100 N | c. | 400 watts | b. | 25 watts | d. | 100 watts |
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14.
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What is the gravitational potential energy of a 54 kg box that is 8.0 m above
the ground?
a. | 5,500 J | c. | 3,400 J | b. | 4,234 J | d. | 550 J |
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15.
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An object weighing 75 N is dropped from the top of a building and falls a
distance of 28 m to the ground. How much work does gravity do on the object from the time it is
dropped to the time it hits the ground?
a. | zero | c. | 2,100 J | b. | 75 J | d. | 4,625 J |
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16.
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Which of the following processes requires the most work?
a. | A 10 kg weight rests on a table. | b. | A person holds a 1 kg weight still with
outstretched arms. | c. | A person lifts a 1 kg weight 1 m off the
floor. |
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17.
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A man pushes a crate along a factory floor by exerting a force of 55 N. If the
crate moves a distance of 4.0 m, how much work does the man perform?
a. | 165 N | c. | zero | b. | 220 J | d. | 145 J |
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18.
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What are the units of power?
a. | watts | c. | joules per second | b. | horsepower | d. | All of the
above |
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19.
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Gravitational potential energy depends on
a. | the mass of the object. | c. | the acceleration due to
gravity. | b. | the height of the object. | d. | All of the above |
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20.
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A medicine ball has a mass of 5 kg and is thrown with a speed of 2 m/s. What is
its kinetic energy?
a. | 100 J | c. | 2,000 J | b. | 10 J | d. | 500 J |
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21.
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A pendulum swings back and forth and has a kinetic energy of 400 J at a
particular point in its path. Which of the following statements is not true?
a. | Both the kinetic and potential energy are decreasing. | b. | The minimum kinetic
energy is zero. | c. | When the kinetic energy is zero, the potential energy will be 400 J
greater. | d. | The potential energy increases when the kinetic energy
decreases. |
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22.
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The brakes on a car exert a frictional force of 6,000 N in getting the car to
stop. If the work done by the brakes is 120,000 J in coming to a stop, how many meters does the car
travel after the driver applies the brakes?
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