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Chapter 5, continued
20. Scientifically speaking, how do you know the cyclist in Figure 4,
on page 113, is accelerating?
21. Another name for acceleration in which velocity increases is
acceleration.
22. Negative acceleration, or acceleration in which velocity
decreases, is also called
.
23. What kind of acceleration is occurring in Figure 5, on page 114?
24. When you are standing completely still at the equator, you are
25. How can you recognize acceleration on a graph?
a.
b.
c.
d.
The
The
The
The
graph
graph
graph
graph
shows distance versus time.
shows time versus distance.
shows velocity changing as time passes.
is a straight line.
Review (p. 114)
Now that you’ve finished Section 1, review what you learned by
answering the Review questions in your ScienceLog.
Section 2: What Is a Force? (p. 115)
Mark the following statements True or False.
1.
All forces have size and direction.
2.
A force is a push or a pull.
3.
Forces are expressed in liters.
34
HOLT SCIENCE AND TECHNOLOGY
Copyright © by Holt, Rinehart and Winston. All rights reserved.
accelerating. True or False? (Circle one.)
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Chapter 5, continued
Forces Act on Objects (p. 115)
4. You can exert a push without there being an object to receive the
push. True or False? (Circle one.)
5. Name three examples of objects that you exert forces on when
you are doing your schoolwork.
6. In which of the following situations is a force being exerted?
(Circle all that apply.)
Forces in Combination (p. 116)
7. In Figure 8, on page 116, how does the net force help the students
move the piano?
CHAPTER 5
8. Suppose the dog on the left in Figure 9, on page 117, increased its
force to 13 N. Which dog would win the tug-of-war? Explain.
▼
▼
▼
Copyright © by Holt, Rinehart and Winston. All rights reserved.
a. A woman pushes the elevator button.
b. A pile of soil sits on the ground.
c. Socks like the ones in Figure 7, on page 116, cling together
when they have just come out of the dryer.
d. Magnets stick to the refrigerator.
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35
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Lesson
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Chapter 5, continued
Unbalanced and Balanced Forces (p. 117)
9. Why is it useful to know the net force?
10. Forces are unbalanced when the net force is not equal to
.
11. To start or change the motion of an object, you need a(n)
force. (balanced or unbalanced)
12. Forces are balanced when the net force applied to an object is
zero.
(less than, greater than, or equal to)
Review (p. 118)
Now that you’ve finished Section 2, review what you learned by
answering the Review questions in your ScienceLog.
Section 3: Friction: A Force that Opposes Motion (p. 119)
1. What force is responsible for the painful difference between sliding on grass and sliding on pavement?
The Source of Friction (p. 119)
2. Friction occurs when the hills and valleys of two surfaces stick
together. True or False? (Circle one.)
3. Pavement creates more friction than grass. Why is that?
36
HOLT SCIENCE AND TECHNOLOGY
Copyright © by Holt, Rinehart and Winston. All rights reserved.
13. Are the forces on the cards in Figure 10 balanced? How do you
know?
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Lesson
Name _______________________________________________ Date ________________ Class______________
Chapter 5, continued
20. Scientifically speaking, how do you know the cyclist in Figure 4,
on page 113, is accelerating?
Sample answer: A change in velocity means acceleration. Because the
cyclist’s velocity increased from 1 m/s south to 5 m/s south, I know that
the cyclist is accelerating.
21. Another name for acceleration in which velocity increases is
positive
acceleration.
22. Negative acceleration, or acceleration in which velocity
decreases, is also called
deceleration
.
23. What kind of acceleration is occurring in Figure 5, on page 114?
Centripetal acceleration is occurring.
24. When you are standing completely still at the equator, you are
25. How can you recognize acceleration on a graph?
a.
b.
c.
d.
The
The
The
The
graph
graph
graph
graph
shows distance versus time.
shows time versus distance.
shows velocity changing as time passes.
is a straight line.
Review (p. 114)
Now that you’ve finished Section 1, review what you learned by
answering the Review questions in your ScienceLog.
Section 2: What Is a Force? (p. 115)
Mark the following statements True or False.
1.
True
All forces have size and direction.
2.
True
A force is a push or a pull.
3.
False
Forces are expressed in liters.
34
HOLT SCIENCE AND TECHNOLOGY
Copyright © by Holt, Rinehart and Winston. All rights reserved.
accelerating. True or False? (Circle one.)
Menu
Print
Lesson
Name _______________________________________________ Date ________________ Class______________
Chapter 5, continued
Forces Act on Objects (p. 115)
4. You can exert a push without there being an object to receive the
push. True or False? (Circle one.)
5. Name three examples of objects that you exert forces on when
you are doing your schoolwork.
Accept any reasonable answer. Sample answer: I exert a force on a book
when I open it, I exert a force on the keys of a keyboard when I type, and I
exert a force on a chair when I sit on it.
6. In which of the following situations is a force being exerted?
(Circle all that apply.)
Forces in Combination (p. 116)
7. In Figure 8, on page 116, how does the net force help the students
move the piano?
When the students apply force in the same direction, their forces are
added together to produce a combined net force.
8. Suppose the dog on the left in Figure 9, on page 117, increased its
force to 13 N. Which dog would win the tug-of-war? Explain.
CHAPTER 5
Sample answer: The dog on the left would win the tug-of-war because
the net force would be 1 N in favor of the dog on the left.
▼
▼
▼
Copyright © by Holt, Rinehart and Winston. All rights reserved.
a. A woman pushes the elevator button.
b. A pile of soil sits on the ground.
c. Socks like the ones in Figure 7, on page 116, cling together
when they have just come out of the dryer.
d. Magnets stick to the refrigerator.
DIRECTED READING WORKSHEETS
35
Print
Menu
Lesson
Name _______________________________________________ Date ________________ Class______________
Chapter 5, continued
Unbalanced and Balanced Forces (p. 117)
9. Why is it useful to know the net force?
It will help you determine the effect of the force on the motion of an
object.
10. Forces are unbalanced when the net force is not equal to
zero
.
11. To start or change the motion of an object, you need a(n)
unbalanced
force. (balanced or unbalanced)
12. Forces are balanced when the net force applied to an object is
equal to
zero.
(less than, greater than, or equal to)
13. Are the forces on the cards in Figure 10 balanced? How do you
know?
Review (p. 118)
Now that you’ve finished Section 2, review what you learned by
answering the Review questions in your ScienceLog.
Section 3: Friction: A Force that Opposes Motion (p. 119)
1. What force is responsible for the painful difference between sliding on grass and sliding on pavement?
The force of friction is responsible.
The Source of Friction (p. 119)
2. Friction occurs when the hills and valleys of two surfaces stick
together. True or False? (Circle one.)
3. Pavement creates more friction than grass. Why is that?
Pavement is rougher than grass.
36
HOLT SCIENCE AND TECHNOLOGY
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Yes; if they were unbalanced, the pile of cards would be collapsing.