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by Steven Holzner Physics FOR DUMmIES ‰ 01_554336 ffirs.qxd 11/2/05 11:25 PM Page i by Steven Holzner Physics FOR DUMmIES ‰ 01_554336 ffirs.qxd 11/2/05 11:25 PM Page i Physics For Dummies® Published by Wiley Publishing, Inc. 111 River St. Hoboken, NJ 07030-5774 www.wiley.com Copyright © 2006 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: 2005933603 ISBN-13: 978-0-7645-5433-9 ISBN-10: 0-7645-5433-6 Manufactured in the United States of America 10 9 8 7 6 5 4 3 2 1 1B/RY/RR/QV/IN 01_554336 ffirs.qxd 11/2/05 11:25 PM Page ii About the Author Steven Holzner is an award-winning author of 94 books that have sold over two million copies and been translated into 18 languages. He served on the Physics faculty at Cornell University for more than a decade, teaching both Physics 101 and Physics 102. Dr. Holzner received his Ph.D. in physics from Cornell and performed his undergrad work at MIT, where he has also served as a faculty member. Dedication To Nancy. Author’s Acknowledgments Any book such as this one is the work of many people besides the author. I’d like to thank my acquisitions editor, Stacy Kennedy, and everyone else who had a hand in the book’s contents, including Natalie Harris, Josh Dials, Joe Breeden, et al. Thank you, everyone. 01_554336 ffirs.qxd 11/2/05 11:25 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: Natalie Faye Harris Acquisitions Editor: Stacy Kennedy Copy Editors: Josh Dials, Kristin DeMint Technical Editor: Joseph L. Breeden Editorial Manager: Michelle Hacker Editorial Assistants: Hanna Scott, Nadine Bell, David Lutton Cover Photos: © Getty Images/Photodisc Cartoons: Rich Tennant (www.the5thwave.com) Composition Services Project Coordinator: Maridee Ennis Layout and Graphics: Mary J. Gillot, Denny Hager, Erin Zeltner Proofreaders: Laura Albert, Leeann Harney, Jessica Kramer, Arielle Mennelle, Joe Niesen, Carl William Pierce Indexer: Joan Griffitts Special Help Danielle Voirol 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_554336 ffirs.qxd 11/2/05 11:25 PM Page iv Contents at a Glance Introduction .................................................................1 Part I: Putting Physics into Motion ................................5 Chapter 1: Using Physics to Understand Your World....................................................7 Chapter 2: Understanding Physics Fundamentals .......................................................13 Chapter 3: Exploring the Need for Speed......................................................................25 Chapter 4: Following Directions: Which Way Are You Going? ....................................43 Part II: May the Forces of Physics Be with You.............61 Chapter 5: When Push Comes to Shove: Force ............................................................63 Chapter 6: What a Drag: Inclined Planes and Friction.................................................81 Chapter 7: Circling around Circular Motions and Orbits ............................................99 Part III: Manifesting the Energy to Work....................117 Chapter 8: Getting Some Work out of Physics............................................................119 Chapter 9: Putting Objects in Motion: Momentum and Impulse..............................137 Chapter 10: Winding Up with Angular Kinetics ..........................................................153 Chapter 11: Round and Round with Rotational Dynamics........................................173 Chapter 12: Springs-n-Things: Simple Harmonic Motion ..........................................189 Part IV: Laying Down the Laws of Thermodynamics.....205 Chapter 13: Turning Up the Heat with Thermodynamics .........................................207 Chapter 14: Here, Take My Coat: Heat Transfer in Solids and Gases.......................219 Chapter 15: When Heat and Work Collide: The Laws of Thermodynamics ............235 Part V: Getting a Charge out of Electricity and Magnetism.........................................................251 Chapter 16: Zapping Away with Static Electricity......................................................253 Chapter 17: Giving Electrons a Push with Circuits ....................................................271 Chapter 18: Magnetism: More than Attraction...........................................................287 Chapter 19: Keeping the Current Going with Voltage................................................305 Chapter 20: Shedding Some Light on Mirrors and Lenses........................................323 02_554336 ftoc.qxd 11/2/05 11:24 PM Page v Part VI: The Part of Tens ...........................................339 Chapter 21: Ten Amazing Insights on Relativity.........................................................341 Chapter 22: Ten Wild Physics Theories.......................................................................349 Glossary...................................................................355 Index .......................................................................361 02_554336 ftoc.qxd 11/2/05 11:24 PM Page vi Table of Contents Introduction..................................................................1 About This Book...............................................................................................1 Conventions Used in This Book .....................................................................2 What You’re Not to Read.................................................................................2 Foolish Assumptions .......................................................................................2 How This Book Is Organized...........................................................................2 Part I: Putting Physics into Motion ......................................................3 Part II: May the Forces of Physics Be with You ..................................3 Part III: Manifesting the Energy to Work..............................................3 Part IV: Laying Down the Laws of Thermodynamics.........................3 Part V: Getting a Charge out of Electricity and Magnetism...............3 Part VI: The Part of Tens .......................................................................4 Icons Used in This Book..................................................................................4 Where to Go from Here....................................................................................4 Part I: Putting Physics into Motion.................................5 Chapter 1: Using Physics to Understand Your World . . . . . . . . . . . . . . .7 What Physics Is All About...............................................................................7 Observing Objects in Motion..........................................................................8 Absorbing the Energy Around You ................................................................9 Feeling Hot but Not Bothered.......................................................................10 Playing with Charges and Magnets..............................................................10 Preparing for the Wild, Wild Physics Coming Up.......................................11 Chapter 2: Understanding Physics Fundamentals . . . . . . . . . . . . . . . . .13 Don’t Be Scared, It’s Only Physics ...............................................................14 Measuring the World Around You and Making Predictions......................15 Don’t mix and match: Keeping physical units straight....................16 From meters to inches and back again: Converting between units................................................................17 Eliminating Some Zeros: Using Scientific Notation....................................20 Checking the Precision of Measurements...................................................21 Knowing which digits are significant.................................................21 Estimating accuracy.............................................................................22 Arming Yourself with Basic Algebra ............................................................23 Tackling a Little Trig ......................................................................................23 02_554336 ftoc.qxd 11/2/05 11:24 PM Page vii Chapter 3: Exploring the Need for Speed . . . . . . . . . . . . . . . . . . . . . . . .25 Dissecting Displacement...............................................................................26 Examining axes .....................................................................................27 Measuring speed ..................................................................................28 Speed Specifics: What Is Speed, Anyway?...................................................29 Reading the speedometer: Instantaneous speed .............................30 Staying steady: Uniform speed ...........................................................30 Swerving back and forth: Nonuniform motion.................................30 Busting out the stopwatch: Average speed ......................................31 Pitting average speed versus uniform motion..................................31 Speeding Up (or Down): Acceleration.........................................................33 Defining acceleration ...........................................................................33 Determining the units of acceleration ...............................................33 Positive and negative acceleration ....................................................35 Average and instantaneous acceleration ..........................................36 Uniform and nonuniform acceleration ..............................................37 Relating Acceleration, Time, and Displacement ........................................37 Not-so-distant relations .......................................................................38 Equating more speedy scenarios .......................................................39 Linking Speed, Acceleration, and Displacement........................................40 Chapter 4: Following Directions: Which Way Are You Going? . . . . . .43 Conquering Vectors .......................................................................................43 Asking for directions: Vector basics ..................................................44 Putting directions together: Adding vectors ....................................45 Taking distance apart: Subtracting vectors ......................................46 Waxing Numerical on Vectors.......................................................................47 Breaking Up Vectors into Components .......................................................49 Finding vector components given magnitudes and angles.............49 Finding magnitudes and angles given vector components.............51 Unmasking the Identities of Vectors............................................................53 Displacement is a vector .....................................................................54 Velocity is another vector ...................................................................54 Acceleration: Yep, another vector......................................................55 Sliding Along on Gravity’s Rainbow: A Velocity Exercise..........................57 Part II: May the Forces of Physics Be with You .............61 Chapter 5: When Push Comes to Shove: Force . . . . . . . . . . . . . . . . . . .63 Forcing the Issue ............................................................................................63 For His First Trick, Newton’s First Law of Motion .....................................64 Getting it going: Inertia and mass ......................................................65 Measuring mass....................................................................................65 Ladies and Gentlemen, Newton’s Second Law of Motion .........................66 Naming units of force...........................................................................67 Gathering net forces.............................................................................67 Physics For Dummies viii 02_554336 ftoc.qxd 11/2/05 11:24 PM Page viii