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Chapter 8
Work and Machines
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Chapter 8
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1. Patrick is evaluating saws to buy for his lumber mill.
He calculates work inputs and outputs for each saw.
Which saw has the highest mechanical efficiency?
A saw A
B saw B
C saw C
D saw D
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Chapter 8
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1. Patrick is evaluating saws to buy for his lumber mill.
He calculates work inputs and outputs for each saw.
Which saw has the highest mechanical efficiency?
A saw A
B saw B
C saw C
D saw D
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Chapter 8
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2. Which of these common objects is a third-class
lever?
A stapler
B chisel
C seesaw
D bottle opener
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2. Which of these common objects is a third-class
lever?
A stapler
B chisel
C seesaw
D bottle opener
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3. How does a simple machine decrease the required
input force?
A by changing the direction of the input force
B by increasing the distance through which the output
force is exerted
C by increasing the distance through which the input
force is exerted
D by decreasing the amount of work that is required
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3. How does a simple machine decrease the required
input force?
A by changing the direction of the input force
B by increasing the distance through which the output
force is exerted
C by increasing the distance through which the input
force is exerted
D by decreasing the amount of work that is required
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4. Kristin is looking for a doorknob that is hard to turn to
keep her baby brother out of her room. Which of the
following doorknobs should she choose?
A a doorknob with a wheel radius of 5 cm and an axle
radius of 4 cm
B a doorknob with a wheel radius of 6 cm and an axle
radius of 2 cm
C a doorknob with a wheel radius of 3 cm and an axle
radius of 0.5 cm
D a doorknob with a wheel radius of 4 cm and an
axle radius of 3 cm
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4. Kristin is looking for a doorknob that is hard to turn to
keep her baby brother out of her room. Which of the
following doorknobs should she choose?
A a doorknob with a wheel radius of 5 cm and an axle
radius of 4 cm
B a doorknob with a wheel radius of 6 cm and an axle
radius of 2 cm
C a doorknob with a wheel radius of 3 cm and an axle
radius of 0.5 cm
D a doorknob with a wheel radius of 4 cm and an
axle radius of 3 cm
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5. A wheelchair ramp is 5.2 m long and 0.8 m high.
What is the ramp’s mechanical advantage?
A 4.2
B 4.4
C 5.2
D 6.5
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5. A wheelchair ramp is 5.2 m long and 0.8 m high.
What is the ramp’s mechanical advantage?
A 4.2
B 4.4
C 5.2
D 6.5
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6. Which of the following is true about the way a screw
works?
A A small input force is applied over a short distance.
B A large input force is applied over a short distance.
C A small input force is applied over a long distance.
D A large input force is applied over a long distance.
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6. Which of the following is true about the way a screw
works?
A A small input force is applied over a short distance.
B A large input force is applied over a short distance.
C A small input force is applied over a long distance.
D A large input force is applied over a long distance.
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7. In this movable pulley, the input force is 20 N. What
is the output force?
A 10 N
B 20 N
C 40 N
D 80 N
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7. In this movable pulley, the input force is 20 N. What
is the output force?
A 10 N
B 20 N
C 40 N
D 80 N
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8. A screwdriver is used to open a paint can. How are
the magnitudes and directions of the input and output
forces related?
A The output force is greater than the input force, and
the directions of the forces are opposite.
B The output force is less than the input force, and the
directions of the forces are opposite.
C The output force is greater than the input force, and
the direction of both forces is the same.
D The output force is less than the input force, and the
direction of both forces is the same.
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8. A screwdriver is used to open a paint can. How are
the magnitudes and directions of the input and output
forces related?
A The output force is greater than the input force, and
the directions of the forces are opposite.
B The output force is less than the input force, and the
directions of the forces are opposite.
C The output force is greater than the input force, and
the direction of both forces is the same.
D The output force is less than the input force, and the
direction of both forces is the same.
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9. Which of the following is true of a simple machine in
which the output force is greater than the input force?
A The mechanical advantage is less than 1.
B The directions of input and output forces must be the
same.
C The amount of work required to accomplish a task is
decreased.
D The input force is exerted over a larger distance than
the output force is.
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9. Which of the following is true of a simple machine in
which the output force is greater than the input force?
A The mechanical advantage is less than 1.
B The directions of input and output forces must be the
same.
C The amount of work required to accomplish a task is
decreased.
D The input force is exerted over a larger distance than
the output force is.
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10. A wheelbarrow is a second-class lever. Its wheel is
the fulcrum, and its load is carried in a tray. What could
be done to a wheelbarrow in order to make lifting and
moving rocks easier?
A the handles could be shortened
B the wheel could be made larger and wider
C the distance between wheel and tray could be
increased
D the tray could be moved so it is above the wheel
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10. A wheelbarrow is a second-class lever. Its wheel is
the fulcrum, and its load is carried in a tray. What could
be done to a wheelbarrow in order to make lifting and
moving rocks easier?
A the handles could be shortened
B the wheel could be made larger and wider
C the distance between wheel and tray could be
increased
D the tray could be moved so it is above the wheel
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11. Jenna is responsible for moving pianos for the
Augusta Symphony. What are two simple machines
that Jenna and her crew could use to move a piano
from the stage in the concert hall onto a high outdoor
stage? Explain how each machine would help make
moving the piano easier.
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11. Answer –
An inclined plane and a block and tackle could be used.
The inclined plane would reduce the input force needed
for moving the piano into a truck or onto a stage,
making it easier to move the piano. However, the piano
would have to be pushed a longer distance than the
height of the stage or truck. The block and tackle would
multiply the input force by 4 (or more), making it
possible to lift the piano with less effort. However, the
rope would have to be pulled four times farther than the
height of the stage or truck bed.
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12. Jeremy is using a hose and a sprinkler to water the
lawn. What simple machines is he using, and how do
these machines make the job easier?
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12. Answer –
A screw and a wheel and axle are being used. Screws
allow the faucet and hose and sprinkler and hose to be
attached to each other easily. A wheel and axle on the
faucet allows the water to be turned on easily.
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