Book cover for Physics

Physics

John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler

ISBN #9781118486894

10th Edition

2,562 Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

The chapter on work and energy introduces the fundamental concepts that link force, energy, and motion. It covers how to compute work from constant and variable forces, demonstrates the work–energy theorem which connects work to changes in kinetic energy, and explains gravitational potential energy. A clear distinction is made between conservative forces, which conserve mechanical energy, and nonconservative forces, which often dissipate energy. Additionally, the measurement and significance of power in doing work are discussed, providing a comprehensive framework for energy transformation in physical systems.

Learning Objectives

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Key Concepts

CONCEPT

DEFINITION

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Example Problems

Example 1

During a tug-of-war, team A pulls on team B by applying a force of $1100 \mathrm{N}$ to the rope between them. The rope remains parallel to the ground. How much work does team A do if they pull team B toward them a distance of $2.0 \mathrm{m} ?$

Example 2

You are moving into an apartment and take the elevator to the 6 th floor. Suppose your weight is $685 \mathrm{N}$ and that of your belongings is $915 \mathrm{N}$. (a) Determine the work done by the elevator in lifting you and your belongings up to the 6 th floor $(15.2 \mathrm{m})$ at a constant velocity. (b) How much work does the elevator do on you alone (without belongings) on the downward trip, which is also made at a constant velocity?

Example 3

The brakes of a truck cause it to slow down by applying a retarding force of $3.0 \times 10^{3} \mathrm{N}$ to the truck over a distance of $850 \mathrm{m} .$ What is the work done by this force on the truck? Is the work positive or negative? Why?

Example 4

A 75.0-kg man is riding an escalator in a shopping mall. The escalator moves the man at a constant velocity from ground level to the floor above, a vertical height of $4.60 \mathrm{m} .$ What is the work done on the man by (a) the gravitational force and (b) the escalator?

Example 5

Suppose in Figure 6.2 that $+1.10 \times 10^{3} \mathrm{J}$ of work is done by the force $\overrightarrow{\mathbf{F}}$ (magnitude $=30.0 \mathrm{N}$ ) in moving the suitcase a distance of $50.0 \mathrm{m}$. At what angle $\theta$ is the force oriented with respect to the ground?
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Step-by-Step Explanations

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Common Mistakes

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