Completion
Complete each
statement.
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1.
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Work, like energy, is measured in ____________________.
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2.
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When a machine is used to perform a task, work output is always
____________________ than work input.
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3.
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To calculate mechanical advantage, you divide the ____________________ force by
the effort force.
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4.
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Unlike a fixed pulley, a movable pulley ____________________ the effort
force.
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5.
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Doorknobs and faucet handles are examples of a simple machine called a
____________________.
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6.
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____________________ is a measure of how much of the work put into a machine is
changed to useful work put out by the machine.
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Short Answer
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7.
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Which of the following could be the mechanical advantage of a third–class
lever: 0.7, 1.5, 10.5, or 3.0?
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8.
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An inventor claims to have built a machine that can produce 120 J of work with
an input of 110 J. Would you believe the inventor's claim? Why or why not?
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9.
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Tin snips, designed for cutting metal, have long handles and short blades.
Shears designed for cutting paper have short handles and long blades. Explain why this is so.
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10.
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What happens to energy when work is done?
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11.
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Explain why the mechanical advantage of a single fixed pulley is always
1.
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12.
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How are work, time, and power related?
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13.
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Explain why adding oil to the moving parts of a machine can increase its
efficiency.
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14.
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Gears are modified wheel-and-axle machines. Explain how to calculate the
mechanical advantage of a pair of gears.
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15.
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Sally and Pete do the same amount of work. Sally does the work in 2.3 hours and
Pete does it in 2.5 hours. Who is more powerful? Explain.
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16.
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Why is actual mechanical advantage less than ideal mechanical advantage?
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17.
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What is the unit of efficiency?
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Problem
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 Figure
5-2
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18.
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Find the ideal mechanical advantage of the second-class lever shown in Figure
5-2.
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19.
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What would be the ideal mechanical advantage of the lever in Figure 5-2 if the
fulcrum were moved 2 m to the right?
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Figure
5-3
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20.
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In Figure 5-3A, what is the ideal mechanical advantage of the inclined
plane?
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21.
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In Figure 5-3A, what is the weight of the block?
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22.
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In Figure 5-3A, what is the amount of work required to move the block along the
total length of the inclined plane?
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23.
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If the weight of the block in Figure 5-3A were doubled, how much work would be
required to move the block along the total length of the inclined plane?
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24.
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If the efficiency of the fixed pulley in Figure 5-3B were 100 percent, how much
force would be required in using the pulley to lift the block off the ground?
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25.
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Calculate the ideal mechanical advantage of a lever that is 6 m long and that
has 4.5 m effort arm.
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26.
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A 24 cm long screwdriver is used as a lever to open a can of paint. If the
fulcrum is 0.5 cm away from the end of the screwdriver, what is the screwdriver's ideal
mechanical advantage?
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27.
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Make a sketch of a possible block-and-tackle arrangement that has a mechanical
advantage of 4.
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