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by Steven Holzner,PhD Physics Workbook FOR DUMmIES ‰ 01_169094 ffirs.qxd 8/23/07 11:59 PM Page i 02_169094 ftoc.qxd 8/23/07 11:59 PM Page vi by Steven Holzner,PhD Physics Workbook FOR DUMmIES ‰ 01_169094 ffirs.qxd 8/23/07 11:59 PM Page i Physics Workbook For Dummies® Published by Wiley Publishing, Inc. 111 River St. Hoboken, NJ 07030-5774 www.wiley.com Copyright © 2007 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 appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400, fax 978-646-8600. 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Library of Congress Control Number: 2007934450 ISBN: 978-0-470-16909-4 Manufactured in the United States of America 10 9 8 7 6 5 4 3 2 1 01_169094 ffirs.qxd 8/23/07 11:59 PM Page ii About the Author Steven Holzner is the award-winning author of more than 100 books, including Physics For Dummies. He did his undergraduate work in physics at Massachusetts Institute of Technology (MIT) and got his PhD from Cornell University. He’s been on the faculty of Cornell for ten years, teaching Physics 101 and Physics 102, as well as on the faculty of MIT. Dedication To Nancy. Author’s Acknowledgments The book you hold in your hands is the result of many people’s work. I would especially like to thank Tracy Boggier, Kelly Ewing, Kathy Simpson, Elizabeth Rea, James Kovalcin, Heather Kolter, and Lynsey Osborn. 01_169094 ffirs.qxd 8/23/07 11:59 PM Page iii Publisher’s Acknowledgments We’re proud of this book; please send us your comments through our Dummies online registration form located at www.dummies.com/register/. Some of the people who helped bring this book to market include the following: Acquisitions, Editorial, and Media Development Project Editor: Kelly Ewing Acquisitions Editor: Tracy Boggier Copy Editors: Elizabeth Rea, Kathy Simpson General Reviewer: James J. Kovalcin Editorial Manager: Michelle Hacker Editorial Supervisor: Carmen Krikorian Editorial Assistants: Erin Calligan Mooney, Joe Niesen, Leeann Harney, David Lutton Cover Photos: © Getty Images/Photodisc Cartoons: Rich Tennant (www.the5thwave.com) Composition Services Project Coordinators: Heather Kolter, Lynsey Osborn Layout and Graphics: Carrie A. Cesavice, Shane Johnson, Stephanie D. Jumper Anniversary Logo Design: Richard Pacifico Proofreaders: Cynthia Fields, Betty Kish Indexer: Infodex Indexing Services, Inc. Special Help: Kathy Simpson Publishing and Editorial for Consumer Dummies Diane Graves Steele, Vice President and Publisher, Consumer Dummies Joyce Pepple, Acquisitions Director, Consumer Dummies Kristin A. Cocks, Product Development Director, Consumer Dummies Michael Spring, Vice President and Publisher, Travel Kelly Regan, Editorial Director, Travel Publishing for Technology Dummies Andy Cummings, Vice President and Publisher, Dummies Technology/General User Composition Services Gerry Fahey, Vice President of Production Services Debbie Stailey, Director of Composition Services 01_169094 ffirs.qxd 8/23/07 11:59 PM Page iv Contents at a Glance Introduction.................................................................................1 Part I : Applying Physics .............................................................5 Chapter 1: Getting Started with Physics ..................................................................................................7 Chapter 2: The Big Three: Acceleration, Distance, and Time ..............................................................25 Chapter 3: Vectors: Knowing Where You’re Headed .............................................................................41 Part II: May the Forces Be with You ...........................................59 Chapter 4: Applying Force ........................................................................................................................61 Chapter 5: Working with Inclined Planes ...............................................................................................81 Chapter 6: Round and Round: Circular Motion ...................................................................................101 Part III: Being Energetic: Work ................................................121 Chapter 7: Working the Physics Way ....................................................................................................123 Chapter 8: Getting Things to Move: Momentum and Kinetic Energy ...............................................143 Chapter 9: Winding It Up: Rotational Kinematics ................................................................................161 Chapter 10: Getting Dizzy with Rotational Dynamics .........................................................................177 Chapter 11: Potential and Kinetic Energy Together: Simple Harmonic Motion ..............................195 Part IV: Obeying the Laws of Thermodynamics ..........................215 Chapter 12: You’re Getting Warm: Thermodynamics .........................................................................217 Chapter 13: Under Pressure: From Solid to Liquid to Gas .................................................................233 Chapter 14: All about Heat and Work ...................................................................................................249 Part V: Zap: Electricity and Magnetism .....................................269 Chapter 15: Static Electricity: Electrons at Rest ..................................................................................271 Chapter 16: Electrons in Motion: Circuits ............................................................................................289 Part VI: The Part of Tens ..........................................................307 Chapter 17: Ten Common Mistakes People Make When Solving Problems .....................................309 Chapter 18: Ten Top Online Physics Tutorials and Resources .........................................................313 Index.......................................................................................315 02_169094 ftoc.qxd 8/23/07 11:59 PM Page v 02_169094 ftoc.qxd 8/23/07 11:59 PM Page vi Table of Contents Introduction .................................................................................1 About This Book ........................................................................................................................1 Conventions Used in This Book ..............................................................................................1 Foolish Assumptions ................................................................................................................1 How This Book Is Organized ....................................................................................................2 Part I: Applying Physics ..................................................................................................2 Part II: May the Forces Be with You ..............................................................................2 Part III: Being Energetic: Work .......................................................................................2 Part IV: Obeying the Laws of Thermodynamics ..........................................................2 Part V: Zap: Electricity and Magnetism ........................................................................2 Part VI: The Part of Tens ................................................................................................3 Icons Used in This Book ...........................................................................................................3 Where to Go from Here .............................................................................................................3 Part I: Applying Physics ...............................................................5 Chapter 1: Getting Started with Physics ...........................................................................7 Measuring the Universe ...........................................................................................................7 Putting Scientific Notation to Work ......................................................................................10 Converting between Units .....................................................................................................12 Converting Distances .............................................................................................................14 Converting Times ....................................................................................................................16 Counting Significant Figures ..................................................................................................17 Coming Prepared with Some Algebra ...................................................................................18 Being Prepared with Trigonometry ......................................................................................20 Answers to Problems about Getting Started with Physics ................................................22 Chapter 2: The Big Three: Acceleration, Distance, and Time .....................................25 From Point A to B: Displacement ..........................................................................................25 Reading That Speedometer ...................................................................................................27 Putting Pedal to Metal: Acceleration ....................................................................................28 Connecting Acceleration, Time, and Displacement ............................................................31 Connecting Speed, Acceleration, and Displacement ..........................................................34 Answers to Problems about Acceleration, Distance, and Time ........................................36 Chapter 3: Vectors: Knowing Where You’re Headed .....................................................41 Creating a Vector .....................................................................................................................41 Understanding Vector Components .....................................................................................43 Finding a Vector’s Components .............................................................................................45 Finding a Vector’s Magnitude and Direction ........................................................................47 Adding Vectors Together .......................................................................................................49 Handling Motion As a Vector .................................................................................................53 Answers to Problems about Vectors ....................................................................................55 02_169094 ftoc.qxd 8/23/07 11:59 PM Page vii Part II: May the Forces Be with You ............................................59 Chapter 4: Applying Force ..................................................................................................61 Newton’s First Law of Motion ................................................................................................61 Newton’s Second Law of Motion ...........................................................................................62 Force Is a Vector ......................................................................................................................65 Calculating Net Force and Acceleration ...............................................................................67 Sorting Out Weight and Mass ................................................................................................69 Newton’s Third Law of Motion ..............................................................................................72 Answers to Problems about Force ........................................................................................74 Chapter 5: Working with Inclined Planes .......................................................................81 Breaking Ramps Up into Vectors ...........................................................................................81 Acceleration and Inclined Planes ..........................................................................................84 Running Down Ramps: Speed ................................................................................................85 It’s a Drag: The Coefficient of Friction ..................................................................................87 Starting from zero: Static friction ................................................................................88 Already in motion: Kinetic friction ..............................................................................89 Static Friction along Ramps ...................................................................................................90 Kinetic Friction along Ramps ................................................................................................92 Acceleration along Ramps Including Friction .....................................................................94 Answers to Problems about Inclined Planes .......................................................................96 Chapter 6: Round and Round: Circular Motion .............................................................101 Converting between Angles .................................................................................................101 Period and Frequency ..........................................................................................................103 Getting into Angular Velocity ...............................................................................................104 Whipping Around with Angular Acceleration ...................................................................107 Connecting Angular Velocity and Angular Acceleration to Angles .................................109 Connecting Angular Acceleration and Angle to Angular Velocity ..................................111 Handling Centripetal Acceleration ......................................................................................112 Getting Forceful: Centripetal Force .....................................................................................114 Answers to Problems about Circular Motion ....................................................................116 Part III: Being Energetic: Work .................................................121 Chapter 7: Working the Physics Way .............................................................................123 A Different Kind of Work .......................................................................................................123 Dealing with the Net Force ...................................................................................................126 Getting Energetic: Kinetic Energy .......................................................................................127 Getting Kinetic Energy from Work ......................................................................................129 Storing Your Energy: Potential Energy ...............................................................................131 Powering It Up .......................................................................................................................133 Answers to Problems about Work ......................................................................................135 Chapter 8: Getting Things to Move: Momentum and Kinetic Energy .......................143 Acting on Impulse .................................................................................................................143 Getting Some Momentum .....................................................................................................145 Relating Impulse and Momentum .......................................................................................146 Conserving Momentum ........................................................................................................148 Conserving Kinetic Energy — or Not ..................................................................................149 Collisions in Two Dimensions .............................................................................................151 Answers to Problems about Momentum and Kinetic Energy ..........................................154 viii Physics Workbook For Dummies 02_169094 ftoc.qxd 8/23/07 11:59 PM Page viii