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Circular Motion and Gravitation
Section Quiz: Torque and Simple Machines
Write the letter of the correct answer in the space provided.
______ 1. What is a measure of the ability of a force to rotate or accelerate an
object around an axis?
a. centripetal force
b. lever arm
c. axis of rotation
d. torque
______ 2. Which of the following statements is correct?
a. The closer the force is to the axis of rotation, the less torque is
produced.
b. The closer the force is to the axis of rotation, the easier it is to
rotate the object.
c. The farther the force is from the axis of rotation, the harder it is to
rotate the object.
d. The farther the force is from the axis of rotation, the less torque is
produced.
______ 3. Where should you push on a door to apply the most torque when
opening the door?
a. close to the top of the door
b. close to the bottom of the door
c. close to the hinges of the door
d. far from the hinges of the door
______ 4. Wrench A is 12 cm long and wrench B is 24 cm long. For a given input
force, how does the maximum torque of wrench A compare to the
maximum torque of wrench B?
a. 1/4 as great
b. 1/2 as great
c. the same
d. 2 times as great
______ 5. Using a machine can allow you to
a. do less work to perform a given task.
b. use less force to do a given amount of work.
c. decrease both the input force and input distance required to do
work.
d. increase both the input force and input distance required to do
work.
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Circular Motion and Gravitation continued
______ 6. What kind of simple machine is like two inclined planes placed backto-back?
a. a lever
b. a screw
c. a wedge
d. a wheel and axle
______ 7. What does mechanical advantage measure?
a. the ratio of input force to output force
b. the ratio of output force to input force
c. the ratio of work input to work output
d. the ratio of work output to work input
______ 8. What does efficiency measure?
a. the ratio of input force to output force
b. the ratio of output force to input force
c. the ratio of work input to work output
d. the ratio of work output to work input
9. Explain why no real machine can have an efficiency of 100%.
10. An 85 kg man and his 35 kg daughter are sitting on opposite ends of a 3.00 m
see-saw. The see-saw is anchored in the center. If the daughter sits 0.20 m
from the left end, how far from the right end would the father have to sit for
the see-saw to be in balance? (g 9.81 m/s2)
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TEACHER RESOURCE
4. d
(6.52 106 m)3
2p
(6.673 1011 N•m2/kg2)(5.97 1024 kg)
5240
s
m
vt G r
(6.673 1011 N•m2/kg2) 5.
6.
7.
8.
9.
(5.97 1024 kg)
7820 m/s
(6.52 106 m)
7 Circular Motion
and Gravitation
TORQUE AND SIMPLE MACHINES
1.
2.
3.
4.
9.
d
5. b
a
6. c
d
7. b
b
8. d
In order for a machine to have 100%
efficiency, the machine would have to
be totally frictionless. Because any real
machine has some friction, some of the
energy input into a real machine is
converted to nonmechanical forms of
energy. As a result, the work output is
always less than the work input.
10. 97 cm from the right end
Given
m1 35 kg
m2 85 kg
d1 1.50 m 0.20 m 1.30 m
g 9.81 m/s2
10.
Solution
Fb rswVswg rswVmg rswl 3g
Solution
F1 m1g (35 kg)(9.81 m/s2) 340 N
F2 m2g (85 kg)(9.81 m/s2) 830 N
tnet F1d1 F2d2 0
F2d2 F1d1
(340 N)(1.30 m)
F1d1
d2 (830 N)
F2
0.53 m
d 1.50 m 0.53 m 0.97 m 97 cm from the right end
Given
weight of displaced water Fg 10.0 N
b
c
c
a
Fluids do not possess definite shape,
because the atoms or molecules in the
fluid are free to move past each other.
Ice is a solid in which the water molecules are bound together in a crystalline arrangement that prevents their
moving past each other. Ice therefore
has definite a shape, and does not flow.
The molecules in liquid water or steam
are able to move past each other, so
that liquid water or steam flows and
has no definite shape, and therefore is
a fluid.
2.2 102 N
The metal is more dense than the salt
water, so it is completely submerged.
The volume of the displaced salt water
(Vsw) equals the volume of the metal
(Vm).
Given
rsw 1.025 103 kg/m3
l 1.3 cm
g 9.81 m/s2
Fb (1.025 103 kg/m3)(1.3 cm)3
1m 3
(9.81 m/s2) 100 cm
2
Fb 2.2 10 N
8 Fluid Mechanics
FLUID PRESSURE
1. c
2. a
3. c
Given
P = 8.0 104 Pa
A = 1.0 102 m2
Solution
F PA (8.0 104 Pa)(1.0 102 m2)
8.0 102 N
4. b
8 Fluid Mechanics
FLUIDS AND BUOYANT FORCE
1. a
2. d
3. a
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Holt Physics
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Answer Key