Third EdiTion Physics - Pearson Education

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Third EdiTionphysicsFOR SCIENTISTS AND ENGINEERSa strategic approachWITH MODERN PHYSICSrandall d. knightCalifornia Polytechnic State UniversitySan Luis ObispoBoston Columbus Indianapolis New York San Francisco Upper Saddle RiverAmsterdam Cape Town Dubai London Madrid Milan Munich Paris Montreal TorontoDelhi Mexico City Sao Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo7583 Knight FM NASTA ppi-xxxi.indd 110/18/11 9:54 AM

Publisher:Senior Development Editor:Senior Project Editor:Assistant Editor:Media Producer:Senior Administrative Assistant:Director of Marketing:Executive Marketing Manager:Managing Editor:Production Project Manager:Production Management, Composition,and Interior Design:Illustrations:Cover Design:Manufacturing Buyer:Photo Research:Image Lead:Cover Printer:Text Printer and Binder:Cover Image:Photo Credits:James SmithAlice Houston, Ph.D.Martha SteelePeter AlstonKelly ReedCathy GlennChristy LeskoKerry McGinnisCorinne BensonBeth CollinsCenveo Publisher Services/Nesbitt Graphics, Inc.Rolin GraphicsYvo Riezebos DesignJeff SargentEric SchraderMaya MelenchukLehigh-PhoenixR.R. Donnelley/Willard Composite illustration by Yvo Riezebos DesignSee page C-1Library of Congress Cataloging-in-Publication DataKnight, Randall Dewey.Physics for scientists and engineers : a strategic approach / randall d. knight. -- 3rd ed.p. cm.Includes bibliographical references and index.ISBN 978-0-321-74090-81. Physics--Textbooks. I. Title.QC23.2.K654 2012530--dc232011033849ISBN-13: 978-0-132-83212-0 ISBN-10: 0-132-83212-7 (High School binding)Copyright 2013, 2008, 2004 Pearson Education, Inc. All rights reserved. Manufactured in the UnitedStates of America. This publication is protected by Copyright, and permission should be obtainedfrom the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmissionin any form or by any means, electronic, mechanical, photocopying, recording, or likewise. To obtainpermission(s) to use material from this work, please submit a written request to Pearson Education, Inc.,Permissions Department, 1900 E. Lake Ave., Glenview, IL 60025. For information regarding permissions,call (847) 486-2635.Many of the designations used by manufacturers and sellers to distinguish their products are claimed astrademarks. Where those designations appear in this book, and the publisher was aware of a trademarkclaim, the designations have been printed in initial caps or all caps.MasteringPhysics is a trademark, in the U.S. and/or other countries, of Pearson Education, Inc. or itsafffiliates.1 2 3 4 5 6 7 8 9 10—DOW—15 14 13 12 11www.PearsonSchool.com/Advanced7583 Knight FM NASTA ppi-xxxi.indd 210/24/11 3:22 PM

Brief ContentsPart I Newton’s LawsChapter 1Chapter 2Chapter 3Chapter 4Chapter 5Chapter 6Chapter 7Chapter 8Concepts of Motion 2Kinematics in One Dimension 33Vectors and Coordinate Systems 69Kinematics in Two Dimensions 85Force and Motion 116Dynamics I: Motion Along a Line 138Newton’s Third Law 167Dynamics II: Motion in a Plane 191Part II Conservation LawsChapter 9 Impulse and Momentum 220Chapter 10 Energy 245Chapter 11 Work 278Part III Applications ofNewtonian MechanicsChapter 12Chapter 13Chapter 14Chapter 15Rotation of a Rigid Body 312Newton’s Theory of Gravity 354Oscillations 377Fluids and Elasticity 407Part IV ThermodynamicsChapter 16 A Macroscopic Descriptionof Matter 444Chapter 17 Work,Heat, and the First Lawof Thermodynamics 469Chapter 18 The Micro/Macro Connection 502Chapter 19 Heat Engines and Refrigerators 526Part V Waves and OpticsChapter 20Chapter 21Chapter 22Chapter 23Chapter 24Traveling Waves 560Superposition 591Wave Optics 627Ray Optics 655Optical Instruments 694Part VI Electricity andMagnetismChapter 25Chapter 26Chapter 27Chapter 28Chapter 29Chapter 30Chapter 31Chapter 32Chapter 33Chapter 34Electric Charges and Forces 720The Electric Field 750Gauss’s Law 780The Electric Potential 810Potential and Field 839Current and Resistance 867Fundamentals of Circuits 891The Magnetic Field 921Electromagnetic Induction 962Electromagnetic Fieldsand Waves 1003Chapter 35 AC Circuits 1033Part VII Relativity and QuantumPhysicsChapter 36 Relativity 1060Chapter 37 The Foundations of ModernPhysics 1102Chapter 38 Quantization 1125Chapter 39 Wave Functions andUncertainty 1156Chapter 40 One-Dimensional QuantumMechanics 1179Chapter 41 Atomic Physics 1216Chapter 42 Nuclear Physics 1248Appendix AAppendix BAppendix CAppendix DMathematics Review A-1Periodic Table of Elements A-4Atomic and Nuclear Data A-5ActivPhysics OnLine Activities andPhET Simulations A-9Answers to Odd-Numbered Problems A-11iii7583 Knight FM NASTA ppi-xxxi.indd 310/21/11 4:16 PM

Builds problem-solving skills and confidence through a carefully structured and research-proven programof problem-solving techniques and practice materials.10.4 . Restoring Forces and Hooke’s LawAt the heart of the problem-solving instruction is the consistent4-step MODEL/ VISUALIZE/ SOLVE/ ASSESS approach, usedthroughout the book and all supplements. Problem-SolvingStrategies provide detailed guidance for particular topics andcategories of problems, often drawing on key skills outlinedin the step-by-step procedures of Tactics Boxes. ProblemSolving Strategies and Tactics Boxes are also illustrated indedicated MasteringPhysics Skill-Builder Tutorials.e r 9 . Impulse and Momentum106 c h a p t e r 4 . Kinematics in Two DimensionsPRoBleM-solvINGPROBLEM-SOLVINGsTRATeGY 10.1STRATEGY1Conservation of mechanical energyChoose a system that is isolated and has no friction or other losses ofmechanical energy.MoDelMODELvIsUAlIZeVISUALIZE2 268c h aDrawp t e ra before-and-after10 . Energy pictorial representation. Define symbols, listknown values, and identify what you’re trying to find.3The mathematical representation is based on the law of conservation of(vix)2M 0 m/s, as expected,mechanical energy:solveSOLVEbecause we chose a moball2wouldbeatrest.Kf Uf Ki UiFIGURe 10.35b now shows a situation—with ball 2 iniAssess Check that your result has the correct units, is reasonable, and answers4 ASSESSuse Equations 10.42 to find the post-collision velocitiethe question.Thus vt vr and at ar are analogous equations for the tangential velocity andTACTICs Drawing a n. In Example4.14, wherewe found the roulette ball to have angularBoX 9.1Exercise 8acceleration a -1.89 rad/s 2, its tangential acceleration was (v )m 1 - m2(v ) 1.72fx 1Mix 1Mat ar ( -1.89rad/s“Before”)(0.15 m) and-0.28“After,”m/s 21 Sketch the situation. Use two drawings, labeledto STOP TO THINK 10.3 A box slides along them1 m2ccbbshow the objects before they interact and again after they interact.frictionless surface shown in the figure. IteXAMPle 4.15 Analyzing rotational dataaa2 Establish a coordinate system. Select your axes to match the motion. is releasedfromrest at theposition shown.2m1You’ve been assigned the task of measuring the start-up characa 2m. If the graph is not a straight line, our observationofWorkedExampleswalk the student veralseconds,whenwhether it curvesupwarddownward willbeforetell us whetherthe highest point the box reaches on theand fortheorvelocities Define symbols. Define symbols for the masses(vfx)2M (vix)1M 6.7Is thethe motor has reached full speed, you know that the angular ular acceleration us increasing or decreasing.m1 m2and after the interaction. Position and time arenot needed.2otherceleration will be zero, but you hypothesize that the angular acFIGURe 4.39 is the graph of u versus t , and it confirmsour side at level a, level b, or level c?reasoning and common pitfalls to avoid.4 Listinformation.valueshypothesisof quantitiesthatstartsareupknownfromangular ac celerationmay beknownconstant duringthe first couple ofGivesecondstheas thethat the motorwith constantmotor speed increases. To find out, you attach a shaft encoder toceleration. The best-fit line, found using a spreadsheet, givesthe problem statement or that can be foundquickly with simple geometry orReferenceframethe 3.0-cm-diameter axle. A shaft encoder is a device that convertsa slope of 274.6 /s 2. The units come not from the spreadsheetNEW! Data-based Examples (shownhere)help M hasn’t changed—it’s still rthanthe( )picturesfor we’rethe angularunitpositionof a shaft or axle toa signal that can be read picturesbybut byat the unitsof riseover run (s 2 because3.0m/s—butthecollision has changed both balls’ velo2a computer. After setting the computer program to read four 10.4Restoring Forces and Hooke’s Lawlawgraphing t ononthethex-axis).Thus theaccelerationisdynamics problems, so listing known informationsketchisangularadequate.a second, you start the motor and acquire the following data:p radTo finish, we need to transform the post-collision ve25 Identify the desired unknowns. What quantity 9.6 rad/sa 549.2 /s 2 *will allowor2mquantitiesyou laboratorydata.FIGURe 10.13 A hanging mass streIf you stretch a rubber band, a force tries to pull the rubber band back to its equilibrium, FIGURE180Time (s)Angle ( )lab frame L. We can do so with another application of2to answerthe question?These should havebeendefinedstep3. to SI units of rad/s180 inp radto convert.wherewe usedor unstretched,length. A force that restores a system to an equilibrium position is called a spring of equilibrium length L 00.0006 If appropriate,draw16 a momentum bar FIGURechart4.39toGraphclarifythe situationandshaft. 0.25of u versust 2 for the motora restoring force. Systems that exhibit restoring forces are called elastic. The most basic length L. (vafxspring,)1M (vx)ML 1.7 m/s (-3.0FIGURe 10.36The signs.u ( )fx)1Lexamplesof elasticityare things like springsand rubber bands. If(vyoustretch0.75161700intension-likethe lab riestore-expandto itsy274.6x0.1(vfx)2L (vfx)2M (vx)ML 6.7 ( -3.0 mExercises 17–191.00267Them/sspring’s600equilibrium length. Other examples of elasticity and restoring forces abound. The steel1.25428restoring 620400FIGURe 10.36 shows the outcome 0of the collision in the labthe pull of gravity.NoTe The generic subscripts i and f, for initial and final, are adequate in equalibrium after your car passes by. Nearly everything that stretches, compresses, flexes,a. Do the data support your hypothesis of a constant angular ac300L(vfx )1L 1.3 m/s(vfx )2L 3.7 m/sthat theseBest-fitlinetions forsimpleproblem,but usingceleration?If so,awhatis the angularacceleration?If not, isnumericalthebends, or twists exhibits a restoring force and can be calledelastic. final velocities do, indeed, conserve both mo200 subscripts, such as v1x and v2x, willangular acceleration increasing or decreasing with time?help keep all the symbols straight in more complexproblems.We’re going to use a simple spring as a prototype of elasticity. Suppose you have100b. A 76-cm-diameter blade is attached to the motor shaft. At whatDisplacementt a(s spring)0whose equilibrium length is L 0. This is the length of the spring when it istime does the acceleration of the tip of the blade reach 10 m/s 2?s L L00.00.51.01.52.02.5neither pushing nor pulling. If you now stretch the spring to length L, how hard does it1 MoDel The axle is rotating with nonuniform circular motion. b. The magnitude of the linear acceleration is1 Hitting a baseballModel the tip of the blade as a particle.pull back? One way to find out is to attach the spring to a bar, as shown in FIGUREFIGURe 10.13,The relaxedA block of mass mat2a 2ar2 4.38 shows that the blade tip has both a tangeneXAMPleA reboundingpendulumrepresentation.20 m/s. FIGUReeball is thrown with a speed2of vIsUAlIZeIt is hitstraight vIsUAlIZe FIGURe 9.8 is a before-and-after pictorialthenCHAlleNGeto hang a massm from10.10the spring.The mass stretchesthe spring to length L.spring hasstretches the springtial and a radial stanttangentialacd the pitcher at a speed of 40 m/s. The interaction force The steps from Tactics Box 9.1 are explicitly noted. Because Fx LengthslengthLL.to e will assumethatthe collisionceleration, and the tangential acceleration of the blade tip is A 2000 g steel ball hangs on a 1.0-m-long string. The ball is upulledFIGURe 4.38 Pictorial representation of the axle and blade.e ball and the bat is shown in FIGURe 9.7. What maxi- is positive (a force to the right), we know the2 ball was initiallyThemass hangsin staticequilibrium,so the upwardspringforce Fsp exactly balat ar (9.6 rad/s )(0.38 m) 3.65 m/s fthe papeu 45 angle,u thenu released. At theFmax does the bat exert on the ball? What is the average moving toward the left and is hit back toward the right. Thus we ances the downward gravitational force F to give F 0. That is,We were careful to use the blade’s radius, not its diameter, andGnet2210.4 . Restoring Forces and Hooke’s LawThe interactioneen the baseballt.NEW!multiple concepts and use moreincreases,sophisticatedreasoning.and the total accelerationreaches 10 m/ssolveFmaxwhenswings down as a pendulum. Second, the ball and paperweight and as thespball reachesits highestto the displacementof thepospa has 9.31m/sNEW! The Mastering Study AreavalsoVideoTutorcreatedby RandyCollegethat the quantitygraphedalong Knight’sthe horizontalaxis isPhysicss L co-authors- L . This is the dis 4.95rad/s Solutions, from equilibrium.r force2.5 paperweightmB 0.38px Jx area underAthecurvehave a collision. Steel balls bounce off each other very0 well, so A and theB, so mA tancethatt

randall d. knight California Polytechnic State University San Luis Obispo Boston Columbus Indianapolis New York San Francisco Upper Saddle River Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montreal Toronto Delhi Mexico City Sao Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo WITH MODERN PHYSICS 7583_Knight_FM_NASTA_ppi-xxxi.indd 1 10/18/11 9:54 AM.