Multiple Choice
Identify the
choice that best completes the statement or answers the question.
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1.
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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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2.
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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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3.
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What is the work output by a 92% efficient wheel and axle when 75 J of work is
input?
a. | 67 J | c. | 75 J | b. | 69 J | d. | 81.5 J |
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4.
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An 84% efficient single pulley is used to lift a 230 kg piano 3.5 m. How much
work must be input?
a. | 676 J | c. | 6.6 x 103 J | b. | 9.6 x 102
J | d. | 9.4 x 103
J |
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5.
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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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6.
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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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7.
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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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8.
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A machine is a device that
a. | requires less work to do a given task. | b. | decreases the amount of work done by a given
force. | c. | increases energy. | d. | can multiply and change the direction of an
input force. |
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9.
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What is the mechanical advantage of a single, fixed pulley?
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10.
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An inclined plane
a. | changes the direction of the force only. | b. | changes the
magnitude of the force only. | c. | changes both the magnitude and the direction of
the force. | d. | decreases the amount of work done. |
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11.
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Which of the following is a compound machine?
a. | a wheel and axle | c. | a pair of scissors | b. | a pulley | d. | a ramp |
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12.
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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. | 4,300 J | d. | 550 J |
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13.
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Which of the following is an example of mechanical energy?
a. | nuclear energy | c. | chemical energy | b. | potential energy | d. | light energy |
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14.
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The primary source of the sun’s energy is
a. | chemical energy. | c. | nuclear fission. | b. | nuclear fusion. | d. | potential
energy. |
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15.
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Which of the following statements is not true?
a. | The energy of a closed system is constant. | b. | The energy of an
open system can increase. | c. | If the kinetic energy of an object decreases,
the nonmechanical energy will decrease. | d. | Energy cannot be created or
destroyed. |
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16.
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The efficiency of a ramp is 75%. If the amount of work input is 240 J, what is
the amount of useful work output?
a. | 320 J | c. | 240 J | b. | 310 J | d. | 180 J |
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17.
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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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18.
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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. | d. | A 10 kg ball is rolled across the floor at a constant speed for a distance of 10
m. |
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19.
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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 N | d. | 145 J |
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20.
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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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21.
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Which of the following is not a simple machine?
a. | a lever | c. | a screw | b. | a pair of scissors | d. | a wheel and
axle |
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22.
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Which of the following is an example of a wheel and axle?
a. | a block and tackle | c. | a screwdriver | b. | a pulley | d. | a nutcracker |
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23.
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Which of the following is not in the inclined plane family?
a. | a wedge | c. | a ramp | b. | a screw | d. | a wheel and
axle |
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24.
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Which of the following statements about work and energy is not
true?
a. | When work is done, energy is transferred or transformed. | b. | Energy may be
defined as the ability to do work. | c. | Work and energy are always
equal. | d. | Work and energy have the same units. |
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25.
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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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26.
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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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27.
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The kind of energy associated with atomic bonds is
a. | nuclear energy. | c. | chemical energy. | b. | light energy. | d. | kinetic energy. |
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28.
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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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29.
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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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30.
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An object has a kinetic energy of 810 J after falling a certain distance. If the
mass of the object is 20 kg, what is the speed of the object at this time?
a. | 10 m/s | c. | 8 m/s | b. | 9 m/s | d. | 7 m/s |
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