Modified True/False
Indicate
whether the sentence or statement is true or false. If false, change the identified word or
phrase to make the sentence or statement true.
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1.
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Holding a 25-N bag of sugar 1 meter above the floor requires 25 joules of work.
_________________________
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2.
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The
force exerted by a machine is called the output force. _________________________
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3.
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The
mechanical advantage of a machine that changes only the direction of a force is 1.
_________________________
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4.
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Efficiency compares the output work to the output force.
_________________________
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5.
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A
wheel and axle is a compound machine. _________________________
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6.
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A
second-class lever always multiplies distance. _________________________
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7.
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The
ideal mechanical advantage of a wheel and axle is the radius of the wheel times the radius of
the axle. _________________________
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8.
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Your
jaw and teeth act together as a simple machine. _________________________
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9.
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When
you raise your leg, the knee acts as a fulcrum for the upper leg.
_________________________
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10.
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You
do work on an object when you lift it from the floor to a shelf.
_________________________
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Essay
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11.
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A
bricklayer lifts a stack of bricks onto his shoulder, carries it across a room, and then lifts the
bricks onto a ledge above his head. Explain if work is being done in each of these three
situations.
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12.
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Explain how the ideal mechanical advantage and efficiency of a machine determine the
machine’s actual mechanical advantage.
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13.
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A
constant push of 250 N is necessary to slide a crate weighing 400 N along a 2.0-meter-long ramp. If
the ramp raises the crate 1.0 m, what is the efficiency of the ramp?
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14.
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Why
is it more difficult to steer a bike when your hands are close together on the handlebars than when
they are far apart?
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15.
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The
output force of a lever with an ideal mechanical advantage of 3 is used as the input force of a
pulley system with an ideal mechanical advantage of 2. What is the ideal mechanical advantage of the
compound machine? Explain.
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16.
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When
you bite with your front teeth, your jaw acts as a third-class lever. As you chew with your back
teeth, your jaw acts as a second-class lever. Explain how your jaw can act as two different classes
of levers and how the ideal mechanical advantage of each helps you bite and chew food.
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17.
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Explain why wedges and screws are actually types of inclined planes.
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18.
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You
push a food tray 1.5 m along a cafeteria table with a constant force of 18 N. How much work do you
do?
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