Force and Motion
An Illustrated Guide to Newton's Laws
Publication Year: 2009
Published by: The Johns Hopkins University Press
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Newtonian mechanics, the subject of this book, is no longer considered a fundamental theory of nature.We live in a world of quantum theory and nanotechnology. But ask a physicist of today, even a quantum physicist, to explain how a curve ball works, and he or she will certainly use the methods and concepts of Newtonian mechanics to do so. Newtonian...
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Index of Key Material
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1 Graphing Relationships
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Being comfortable with graphs is a basic requirement for citizenship in modern society. To become knowledgeable about issues such as global climate change, for example, we have to know how to interpret graphs like the one shown in Figure 1. This figure is a line graph. Line graphs
2 Rates of Change
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Change is at the heart of physics. That’s because physics is the science that seeks to explain why anything happens at all! The physicist wants to know what makes any given situation develop as time progresses. In order to begin to answer this question, it is important to be able to understand change, and rates of change, intuitively as well as quantitatively...
3 Introducing Position and Velocity
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The three basic concepts in the study of motion are position, velocity, and acceleration. We begin our study of motion in earnest with the first two of these concepts: position and velocity...
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In Chapter 3 I explained two kinds of vectors, position (r) and velocity (v). We’ll be working with vectors constantly in this book, so let’s take some time now to learn how to analyze them in detail...
5 Position and Velocity, Revisited
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Chapter 3 introduced a few basic ideas about position and velocity: • An object’s position vector r tells how far from the origin the object is and in what direction. • To draw the position vector, start with the tail at the origin and end with the tip at the location of the object. • An object’s velocity vector v tells how fast the object is moving and in what direction...
6 Introducing Acceleration
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The word acceleration means something different in physics than it does in everyday speech. In everyday speech, acceleration means only “speeding up.” But in physics, speeding up is just one of the meanings of the word acceleration. Strangely enough, in physics acceleration can also mean slowing down! In common speech, slowing down is sometimes...
7 Acceleration as a Rate of Change
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Imagine cruising along in your car with a constant, unchanging velocity vector v. Your car is just humming along, following a straight, flat road, maintaining a constant speed. Bored by the monotony, at risk of falling asleep at the wheel, you decide that you want to change your velocity vector. What are some ways you could do it...
8 Focus on a-Perp
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As the concept map in Chapter 7 (Figure 108) illustrates, there are two basic ways to view the acceleration vector. • As we discussed in Chapter 6, we can view the acceleration vector as an indication of whether an object is speeding up, slowing down, or turning. • Equally well, as we discussed...
9 Case Study: Straight-Line Motion
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Sometimes there are simple situations in which the motion of an object is confined more or less to a straight line. Think of driving a car along a straight (and flat) road, stepping off of a diving board and falling straight down, working a yo-yo straight up and down, or riding on an escalator...
10 The Concept of Force
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In Chapter 6 we saw that in physics the word acceleration means much more than simply “speeding up,” its meaning in everyday speech. Physics also uses other words from everyday speech: words like force, momentum, and energy...
11 Combining Forces That Act on the Same Target
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At any given time, your body is subject to a number of noticeable influences. The earth pulls you down. Your chair pushes you up. The moon and sun tug on you slightly, the other celestial bodies negligibly so. Now a breeze ruffles your hair; the air is exerting a force on you as well. All of these forces can be combined, leading to a single net influence. This net...
12 “Newton‘s Little Law”
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Congratulations! You’ve reached the very threshold of the System of the World. Already you have journeyed across a varied landscape of physics. You have studied rates of change, and also rates of change of rates of change. You have added and subtracted vectors. You have examined...
13 Newton’s Second Law
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“What is mass?” is a profound question. Indeed, modern physical theories such as field theory and string theory are still trying to sort this out. In this book we’ll take the commonsense view Newton himself took: Mass is simply the amount of “material stuff” contained in an object...
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Newton’s Second Law permits us to solve two basic kinds of problems. These problems are in a sense the reverse of one another: • Problem Type 1. By observing the motion of an object, deduce the nature of the forces at work on it. • Problem Type 2. By knowing something about the forces at work on an object, predict its...
15 Newton’s Third Law
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In Chapter 10 I explained that every action is an interaction. You can’t touch without being touched. Newton’s Third Law formalizes this idea and makes it quantitative. Here it is: Newton’s Third Law: If object 1 exerts a force on object 2, object 2 must also exert an equal and opposite force on object...
16 Kinds of Force
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Every force has a type, or kind. For example, the force that the sun exerts on the earth is of the gravitational kind. The force that a magnet exerts on a nail is of the magnetic kind. The force that lifts your hairs after you rub a balloon on your head is of the electrostatic kind. Table 5 lists...
17 Strategies for Applying Newton’s Laws
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In this chapter I’ll suggest some organized strategies that can help you in applying Newton’s Laws to understand physical situations and solve challenging physics problems. But before we get started, let’s talk about attitude...
Appendix: Derivation of Huygens’s Formula
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Answers to Focused Problems
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Index of Problem Situations
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Page Count: 440
Illustrations: 3 halftones, 349 line drawings
Publication Year: 2009