™ g Easier! Making Everythin Physics Es s e n t i a l s Learn: • The fundamentals of force, work, and energy • The components of linear and rotational motion • How to connect physics concepts with the real world Steven Holzner, PhD Author of Quantam Physics For Dummies www.com Physics Essentials FOR DUMmIES ‰ www.com Physics Essentials FOR DUMmIES ‰ by Steven Holzner, PhD with Daniel Wohns www.com Physics Essentials For Dummies® Published by Wiley Publishing, Inc. Hoboken, NJ 07030-5774 www.com Copyright © 2010 by Wiley Publishing, Inc., Indianapolis, Indiana Published by Wiley Publishing, Inc., Indianapolis, Indiana Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appro- priate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.com/go/permissions. Trademarks: Wiley, the Wiley Publishing logo, For Dummies, the Dummies Man logo, A Reference for the Rest of Us!, The Dummies Way, Dummies Daily, The Fun and Easy Way, Dummies.com, Making Everything Easier, and related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc.
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Some content that appears in print may not be available in electronic books. Library of Congress Control Number: 2010925164 ISBN: 978-0-470-61841-7 Manufactured in the United States of America 10 9 8 7 6 5 4 3 2 1 www.com About the Author Steven Holzner is an award-winning author of 94 books that have sold over 2 million copies and been translated into 18 lan- guages. He served on the Physics faculty at Cornell University for more than a decade, teaching both Physics 101 and Physics 102. Holzner received his PhD in physics from Cornell and performed his undergrad work at MIT, where he has also served as a faculty member.com Publisher’s Acknowledgments We’re proud of this book; please send us your comments at http://dummies.
For other comments, please contact our Customer Care Department within the U. at 877-762-2974, outside the U. at 317-572-3993, or fax 317-572-4002. Some of the people who helped bring this book to market include the following: Acquisitions, Editorial, and Composition Services Media Development Project Coordinator: Sheree Montgomery Project Editor: Joan Friedman Layout and Graphics: Carrie A.
Cesavice, Acquisitions Editor: Ronald G. Terry, Christine Williams Lindsay Sandman Lefevere Proofreader: Henry Lazarek Assistant Editor: Erin Calligan Mooney Indexer: Potomac Indexing, LLC Senior Editorial Assistant: David Lutton Technical Editors: Matt Cannon, Gang Xu Senior Editorial Manager: Jennifer Ehrlich Editorial Supervisor and Reprint Editor: Carmen Krikorian Editorial Assistant: Rachelle S. Amick Cover Photos: © Head-off | Dreamstime.com Cartoons: Rich Tennant (www.com) Publishing and Editorial for Consumer Dummies Diane Graves Steele, Vice President and Publisher, Consumer Dummies Kristin Ferguson-Wagstaffe, Product Development Director, Consumer Dummies Ensley Eikenburg, Associate Publisher, Travel Kelly Regan, Editorial Director, Travel Publishing for Technology Dummies Andy Cummings, Vice President and Publisher, Dummies Technology/General User Composition Services Debbie Stailey, Director of Composition Services www.com Contents at a Glance Introduction. 1 Chapter 1: Viewing the World through the Lens of Physics.
5 Chapter 2: Taking Vectors Step by Step. 15 Chapter 3: Going the Distance with Speed and Acceleration. 25 Chapter 4: Studying Circular Motions. 41 Chapter 5: Push-Ups and Pull-Ups: Exercises in Force.
49 Chapter 6: Falling Slowly: Gravity and Friction. 63 Chapter 7: Putting Physics to Work. 77 Chapter 8: Moving Objects with Impulse and Momentum. 95 Chapter 9: Navigating the Twists and Turns of Angular Kinetics.
111 Chapter 10: Taking a Spin with Rotational Dynamics. 127 Chapter 11: There and Back Again: Simple Harmonic Motion. 139 Chapter 12: Ten Marvels of Relativity .com Contents Introduction .1 About This Book. 1 Conventions Used in This Book.
2 Icons Used in This Book. 3 Where to Go from Here. 3 Chapter 1: Viewing the World through the Lens of Physics .5 Figuring Out What Physics Is About. 5 Paying Attention to Objects in Motion.
7 Moving as Fast as You Can: Special Relativity. 8 Measuring Your World. 9 Keeping physical units straight. 10 Converting between units of measurement.
10 Nixing some zeros with scientific notation. 12 Knowing which digits are significant. 12 Chapter 2: Taking Vectors Step by Step .15 Getting a Grip on Vectors. 15 Looking for direction and magnitude.
18 Waxing Numerical on Vectors. 19 Working with Vector Components. 20 Using magnitudes and angles to find vector components .20 Using vector components to find magnitudes and angles. 22 Chapter 3: Going the Distance with Speed and Acceleration .25 From Here to There: Dissecting Displacement.
28 The Fast Track to Understanding Speed and Velocity. 29 How fast am I right now? Instantaneous speed. 30 Staying steady: Uniform speed .com x Physics Essentials For Dummies Changing your speed: Nonuniform motion. 30 Doing some calculations: Average speed.
31 Contrasting average speed and instantaneous speed. 32 Speeding Up (or Slowing Down): Acceleration. 33 Defining our terms. 34 Recognizing positive and negative acceleration.
34 Looking at average and instantaneous acceleration. 35 Accounting for uniform and nonuniform acceleration. 35 Bringing Acceleration, Time, and Displacement Together .36 Locating not-so-distant relations. 37 Equating more speedy scenarios.
38 Putting Speed, Acceleration, and Displacement Together .39 Chapter 4: Studying Circular Motions .41 Understanding Uniform Circular Motion. 41 Creating Centripetal Acceleration. 43 Seeing how centripetal acceleration controls velocity .44 Calculating centripetal acceleration. 44 Finding Angular Equivalents for Linear Equations.
45 Chapter 5: Push-Ups and Pull-Ups: Exercises in Force .49 Reckoning with Force. 49 Objects at Rest and in Motion: Newton’s First Law. 50 Calculating Net Force: Newton’s Second Law. 52 Gathering net forces.
53 Just relax: Dealing with tension. 57 A balancing act: Finding equilibrium. 58 Equal and Opposite Reactions: Newton’s Third Law. 61 Chapter 6: Falling Slowly: Gravity and Friction .63 Dropping the Apple: Newton’s Law of Gravitation.
63 Down to Earth: Dealing with Gravity. 65 Leaning Vertically with Inclined Planes .com Table of Contents xi Facing Friction. 68 Figuring out the normal force. 69 Finding the coefficient of friction.
70 Bringing static and kinetic friction into the mix. 71 Getting moving with static friction. 71 Staying in motion with kinetic friction. 72 Dealing with uphill friction.
73 Calculating the component weight. 74 Determining the force of friction. 74 Chapter 7: Putting Physics to Work .77 Wrapping Your Mind around Work. 77 Pushing your weight.
79 Working Backward: Negative Work. 80 Working Up a Sweat: Kinetic Energy. 81 Breaking down the kinetic energy equation. 83 Using the kinetic energy equation.
84 Calculating kinetic energy by using net force. 85 Saving Up: Potential Energy. 87 Working against gravity. 88 Converting potential energy into kinetic energy.
89 Pitting Conservative against Nonconservative Forces. 90 No Work Required: The Conservation of Mechanical Energy .92 A Powerful Idea: The Rate of Doing Work. 93 Chapter 8: Moving Objects with Impulse and Momentum .95 Feeling a Sudden Urge to Do Physics: Impulse. 97 Connecting Impulse and Momentum.
98 Taking impulse and momentum to the pool hall. 99 Getting impulsive in the rain. 100 Watching Objects Go Bonk: The Conservation of Momentum. 101 Measuring Firing Velocity.
103 Examining Elastic and Inelastic Collisions. 105 Flying apart: Elastic collisions. 106 Sticking together: Inelastic collisions. 106 Colliding along a line.
107 Colliding in two dimensions .com xii Physics Essentials For Dummies Chapter 9: Navigating the Twists and Turns of Angular Kinetics .111 Changing Gears (and Equations) from Linear to Rotational Motion. 111 Tackling Tangential Motion. 112 Calculating tangential speed. 113 Figuring out tangential acceleration.
114 Looking at centripetal acceleration. 115 Applying Vectors to Rotation. 116 Analyzing angular velocity. 116 Working out angular acceleration.
117 Doing the Twist with Torque. 119 Walking through the torque equation. 120 Mastering lever arms. 122 Identifying the torque generated.
123 Realizing that torque is a vector. 124 No Spin, Just the Unbiased Truth: Rotational Equilibrium. 125 Chapter 10: Taking a Spin with Rotational Dynamics .127 Converting Newton’s Second Law into Angular Motion. 127 Moving from tangential to angular acceleration.
129 Bringing the moment of inertia into play. 129 Finding Moments of Inertia for Standard Shapes. 131 Doing Rotational Work and Producing Kinetic Energy. 132 Making the transition to rotational work.
133 Solving for rotational kinetic energy. 134 Going Round and Round with Angular Momentum. 136 Chapter 11: There and Back Again: Simple Harmonic Motion .139 Homing in on Hooke’s Law. 139 Staying within the elastic limit.
140 Exerting a restoring force. 141 Déjà Vu All Over Again: Simple Harmonic Motion. 142 Browsing the basics of simple harmonic motion. 142 Exploring some complexities of simple harmonic motion.
144 Breaking down the sine wave .com Table of Contents xiii Studying the velocity. 149 Including the acceleration. 150 Finding angular frequencies of masses on springs. 152 Examining Energy in Simple Harmonic Motion.
154 Going for a Swing with Pendulums. 156 Chapter 12: Ten Marvels of Relativity .159 Nature Doesn’t Play Favorites. 159 The Speed of Light Is Constant. 160 Time Contracts at High Speeds.
161 Space Travel Slows Down Aging. 162 Length Shortens at High Speeds. 162 Matter and Energy Are Equivalent: E = mc2 .163 Matter + Antimatter Equals Boom. 164 The Sun Is Losing Mass.
164 You Can’t Surpass the Speed of Light. 164 Newton Was Right .com xiv Physics Essentials For Dummies www.com Introduction P hysics is what it’s all about.