Name:______________________________Class:__________________ Date:__________________
Assessment
Circular Motion and Gravitation
Teacher Notes and Answers
7 Circular Motion and Gravitation
TORQUE AND SIMPLE MACHINES
1.
2.
3.
4.
5.
6.
7.
8.
9.
d
a
d
b
b
c
b
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
Solution
2
F1 = m1 g = (35 kg)(9.81 m/s ) =
340 N
2
F2 = m 2 g = (85 kg)(9.81 m/s ) =
830 N
net = F1 d1 + F2 d 2 = 0
F2 d 2 = F1 d1
d2 = F1 d1
F2
=
(340 N )(1.30 m)
(830 N )
= 0.53 m
d = 1.50 m 0.53 m = 0.97 m =
97 cm from the right end
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
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Section Quizzes
Name:______________________________Class:__________________ Date:__________________
Assessment
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.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Physics
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Section Quizzes
Name:______________________________Class:__________________ Date:__________________
Circular Motion and Gravitation continued
_____ 6. What kind of simple machine is like two inclined planes placed
back-to-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)
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Physics
3
Section Quizzes