chapter 5. force and motion - northern highlands regional high … · 2014. 9. 1. · chapter 5....

Chapter 5. Force and MotionChapter 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.

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

Chapter 5. Force and MotionChapter 5. Force and Motion

Chapter 5. Reading QuizzesChapter 5. Reading Quizzes

What is a “net force?”

A. The weight excluding the containerB. The vector sum of all forces in a problemC. The vector sum of all forces acting on an objectD. The vector force applied by a netE. The vector sum of all forces that add up to zero

What is a “net force?”

A. The weight excluding the containerB. The vector sum of all forces in a problemC. The vector sum of all forces acting on an objectD. The vector force applied by a netE. The vector sum of all forces that add up to zero

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.

Which of the following are steps used to identify the forces acting on an object?

A. Draw a closed curve around the systemB. Identify “the system” and “the environment”C. Draw a picture of the situationD. All of the aboveE. None of the above

Which of these is not a force discussed in this chapter?

A. The tension forceB. The orthogonal forceC. The normal forceD. The thrust forceE. None of the above

Which of these is not a force discussed in this chapter?

A. The tension forceB. The orthogonal forceC. The normal forceD. The thrust forceE. None of the above

What is the name of a diagram used to show all forces acting on an object?

A. Motion diagramB. Interaction diagramC. Free-body diagramD. Second-law diagram

What is the name of a diagram used to show all forces acting on an object?

A. Motion diagramB. Interaction diagramC. Free-body diagramD. Second-law diagram

Chapter 5. Basic Content and ExamplesChapter 5. Basic Content and Examples

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.

Tactics: Drawing force vectors

A Short Catalog of Forces

Tactics: Identifying forces

EXAMPLE 5.1 Forces on a bungee jumper

QUESTION:

EXAMPLE 5.1 Forces on a bungee jumper

EXAMPLE 5.2 Forces on a skier

QUESTION:

EXAMPLE 5.2 Forces on a skier

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.

Tactics: Drawing a free-body diagram

EXAMPLE 5.4 An elevator accelerates upward

EXAMPLE 5.5 An ice block shoots across a frozen lake

Chapter 5. Summary SlidesChapter 5. Summary Slides

General Principles

Important Concepts

Key Skills

Chapter 5. Clicker QuestionsChapter 5. Clicker Questions

Two of three forces exerted on an object are shown. The net force points to the left. What is the missing third force?

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 downwardB. The normal force, acting upwardC. The force of the kick, acting in the

direction of motionD. Friction, acting opposite the direction of

motionE. A, B, and D but not C.

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 downwardB. The normal force, acting upwardC. The force of the kick, acting in the

direction of motionD. Friction, acting opposite the direction of

motionE. A, B, and D but not C.

Two rubber bands stretched the standard distance cause an object to accelerate at2 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.

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.

Three forces act on an object. In which direction does the object accelerate?

An elevator suspended by a cable is moving upward and slowing to a stop. Which free-body diagram is correct?

chapter 5. force and motion - northern highlands regional high … · 2014. 9. 1. · chapter 5....

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