Download Chapter 5. Force and Motion Chapter 5. Force and Motion

Chapter 5. Force and Motion
In this chapter we study
causes of motion: Why does
the windsurfer blast across
the water in the way he
does? The combined forces
of the wind, water, and
gravity accelerate him
according to the principles
of dynamics.
Chapter Goal: To establish
a connection between force
and motion.
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Chapter 5. Force and Motion
Topics:
• Force
• A Short Catalog of Forces
• Identifying Forces
• What Do Forces Do? A Virtual Experiment
• Newton’s Second Law
• Newton’s First Law
• Free-Body Diagrams
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Chapter 5. Reading Quizzes
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What is a “net force?”
A. The weight excluding the container
B. The vector sum of all forces in a problem
C. The vector sum of all forces acting on an object
D. The vector force applied by a net
E. The vector sum of all forces that add up to zero
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.
What is a “net force?”
A. The weight excluding the container
B. The vector sum of all forces in a problem
C. The vector sum of all forces acting on an object
D. The vector force applied by a net
E. The vector sum of all forces that add up to zero
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Which of the following are steps used to
identify the forces acting on an object?
A. Draw a closed curve around the system.
B. Identify “the system” and “the environment”.
C. Draw a picture of the situation.
D. All of the above.
E. None of the above.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.
Which of the following are steps used to
identify the forces acting on an object?
A. Draw a closed curve around the system
B. Identify “the system” and “the environment”
C. Draw a picture of the situation
D. All of the above
E. None of the above
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.
Which of these is not a force discussed in
this chapter?
A. The tension force
B. The orthogonal force
C. The normal force
D. The thrust force
E. None of the above
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.
Which of these is not a force discussed in
this chapter?
A. The tension force
B. The orthogonal force
C. The normal force
D. The thrust force
E. None of the above
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.
What is the name of a diagram used to
show all forces acting on an object?
A. Motion diagram
B. Interaction diagram
C. Free-body diagram
D. Second-law diagram
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.
What is the name of a diagram used to
show all forces acting on an object?
A. Motion diagram
B. Interaction diagram
C. Free-body diagram
D. Second-law diagram
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.
Chapter 5. Basic Content and Examples
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What is a force?
• A force is a push or a pull on an object.
• A force is a vector. It has both a magnitude
and a direction.
• A force requires an agent. Something does
the pushing or pulling.
• A force is either a contact force or a long range force. Gravity is the only long-range
force we will deal with until much later in
the book.
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Tactics: Drawing force vectors
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A Short Catalog of Forces
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A Short Catalog of Forces
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A Short Catalog of Forces
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A Short Catalog of Forces
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A Short Catalog of Forces
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A Short Catalog of Forces
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A Short Catalog of Forces
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Tactics: Identifying forces
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Tactics: Identifying forces
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EXAMPLE 5.1 Forces on a bungee jumper
QUESTION:
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EXAMPLE 5.1 Forces on a bungee jumper
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EXAMPLE 5.2 Forces on a skier
QUESTION:
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EXAMPLE 5.2 Forces on a skier
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Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.
Newton’s first law is also known as the law of
inertia. If an object is at rest, it has a tendency to
stay at rest. If it is moving, it has a tendency to
continue moving with the same velocity.
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Tactics: Drawing a free-body diagram
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Tactics: Drawing a free-body diagram
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EXAMPLE 5.4 An elevator accelerates
upward
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EXAMPLE 5.4 An elevator accelerates
upward
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EXAMPLE 5.4 An elevator accelerates
upward
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EXAMPLE 5.4 An elevator accelerates
upward
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EXAMPLE 5.5 An ice block shoots across a
frozen lake
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EXAMPLE 5.5 An ice block shoots across a
frozen lake
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EXAMPLE 5.5 An ice block shoots across a
frozen lake
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EXAMPLE 5.5 An ice block shoots across a
frozen lake
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Chapter 5. Summary Slides
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General Principles
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General Principles
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Important Concepts
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Important Concepts
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Important Concepts
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Key Skills
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Key Skills
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Chapter 5. Clicker Questions
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Two of three forces exerted on an object are
shown. The net force points to the left. What is
the missing third force?
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Two of three forces exerted on an object are
shown. The net force points to the left. What is
the missing third force?
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You’ve just kicked a rock, and it is now
sliding across the ground about 2 meters
in front of you. Which of these forces act
on the ball?
A. Gravity, acting downward
B. The normal force, acting upward
C. The force of the kick, acting in the
direction of motion
D. Friction, acting opposite the direction of
motion
E. A, B, and D but not C.
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You’ve just kicked a rock, and it is now
sliding across the ground about 2 meters
in front of you. Which of these forces act
on the ball?
A. Gravity, acting downward
B. The normal force, acting upward
C. The force of the kick, acting in the
direction of motion
D. Friction, acting opposite the direction of
motion
E. A, B, and D but not C.
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Two rubber bands stretched the standard
distance cause an object to accelerate at
2 m/s2. Suppose another object with twice
the mass is pulled by four rubber bands
stretched the standard length. The
acceleration of this second object is
A. 16 m/s2.
B. 8 m/s2.
C. 4 m/s2.
D. 2 m/s2.
E. 1 m/s2.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.
Two rubber bands stretched the standard
distance cause an object to accelerate at 2
m/s2. Suppose another object with twice the
mass is pulled by four rubber bands
stretched the standard length. The
acceleration of this second object is
A. 16 m/s2.
B. 8 m/s2.
C. 4 m/s2.
D. 2 m/s2.
E. 1 m/s2.
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Three forces act on an object. In which
direction does the object accelerate?
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Three forces act on an object. In which
direction does the object accelerate?
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An elevator suspended by a cable is
moving upward and slowing to a stop.
Which free-body diagram is correct?
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An elevator suspended by a cable is
moving upward and slowing to a stop.
Which free-body diagram is correct?
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