Table Of ContentH^i
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Numerical Data
A: FundamentalConstants B: Practical Data
Speedoflight c 2.99792458 X 108m/sexact TheEarth
Permeabilityofvacuum Mo 4-7T X 10~7N/A2exact Mass 5.98 X 1024kg
Permittivityofvacuum e 8.85418782 X 10~12 F/m Polarradius 6.357 X 103km
Gravitationalconstant G 6.6726 X 10-]I m3/kg-s2 Equatorialradius 6.378 X 103km
Elementarycharge e 1.6021773 X 10^19C Meandensity 5.52 X 103kg/m3
Planck'sconstant h 6.626076 X 10"34Js Rotationalinertia 8.04 X 1037kg-m:
h-bar = h/2ir h 1.054573 X 10"34J-s (aboutrotationaxis)
Avogadro'snumber NA 6.022137 X 1023/mol Magneticfield:
Electronmass rae 9.109390 X 10-J1 kg Horizontalcomponentattheequator 3.2 X 10~5T
Proton mass m 1.672623 X 10^27kg VerticalcomponentatmagneticNpole 6.2 X 10"5T
p
Rydbergconstant R» 1.09737315 X 107/m Magneticdipolemoment 8.1 X 1022A-m2
Finestructureconstant a 7.2973531 X 10 3 Electricfieldatsealevel 130V/m
Ha Hoc 137.03599 Meanoceandepth 3770m
CEllaescstircoanlCeloemctprtoonnrawdaivueslength Arec 22..48216739140069 XX 1100~^1152mm GErsacvaipteatvieolnoaclitayccelerationatsurface 91.18.2mk/ms/2s
Bohrradius «o 5.2917725 X 10-"m
TheSun
Boltzmann'sconstant k 1.38066 X 10~23J/K Radius 6.96 X 10sm
Mass 1.99 X 1030kg
W
Luminosity 3.90 X 1026
Averagesurfacemagneticfield 10~4T
Angularspeed 2.87 X 10 6rad/s
Rotationalinertia 6.0 X 10'6kg-m2
Escapevelocity 618 km/s
TheMoon
MeandistancefromEarth 3.84 X 105km
Eccentricityoforbit 0.0549
Radius 1.738 X 103km
Mass 7.35 X 1022kg
Meandensity 3.34 X 103kg/m3
Thesolarsystem
Semimajor
Mass AXISOF Orbital
(Earth- Radius ORBIT Period
Planet masses) (106m) (109m) (years) Eccentricity
Mercury 0.056 2.44 57.9 0.241 0.206
Venus 0.815 6.05 108 0.615 0.07
Earth 1.00 6.38 149.6 1.00 0.017
Mars 0.107 3.39 227.9 1.88 0.093
Jupiter 317.9 71.4 778.3 11.86 0.048
.
Saturn 95.2 60 1.427 X 103 29.46 0.056
Uranus 14.5 25.9 2.87 X 103 84.01 0.047
Neptune 17.1 24.75 4.497 X 103 164.8 0.009
Pluto 0.002 1.1 5.9 X 103 248 0.250
-
Unit Systems and Conversion Factors
SI Units
Fundamentalunits mass kg kilogram
m
length meter
time s second
electriccurrent A ampere
Supplementaryunit angle rad radian
Somederivedunits force N = kg-m/s2 newton
energy = N-m joule
WJ
power = J/s watt
frequency Hz = 1/s hertz
pressure Pa = N/m2 pascal
charge C = A-s coulomb
V =
electricpotential J/C volt
magneticfield T = N/A-m tesla
magneticflux Wb = T-m2 weber
capacitance F = C/V farad
resistance n = v/a ohm
Selected British Units Miscellaneous Units
length 1 inch = 2.540cm time 1 y « rr X 107s
1 foot = 0.3048 m 1 d = 86400s
1 mile = 1.609km length 1 nauticalmile = 1.852km
mass 1 poundmass (usedintheU.K.) = 0.4536kg speed 1 mph = 0.4470m/s
1 slug (massunitusedintheU.S.) = 14.59kg 1 knot = 0.5145 m/s
1 ton = 2240 lbmass (Britishorlongton) mass 1 u (atomicmass unit) = 1.660 X 10 27 kg
1 U.S. ton = 2000lb mass (shortton) 1 metricton = 1000kg
peonewregry 11 Bhroirtsieshptohweerrma=l7u4n5it.7=W1.055 X 103 J energy 11 ecalleocrtireon=vo4l.t18=J1.60 X 10-l9J
force 1 pound (calledpound-weightin theU.K.) = 4.448 N 1 kilowatt-hour = 3.60 X 1061
pressure 1 lb/in.2 = 6.895 X 103Pa 1 kiloton ofTNT = 4.2 X 1012 1
pressure 1 atmosphere = 1.013 X 105 Pa
1 torr = 133.3 Pa
Selected cgs/Gaussian Units 1 cmHg= 1.333 X 10-' Pa
length 1 cm = 10~2m 1 in. Hg = 3.386 X 103Pa
mass 1 g = 10~3kg volume 1 liter = 10 3m3
fpeornreecsresguyre l11eddryyngn/=ec=m1021~0=7"J05.N1 Pa area l11bUaa.cSrr.eng==al4l1.o00n5=2X83m.1720835mX2 10 m
magneticfield 1 gausscorrespondsto 10~4T angle 1°= 1.745 X 10~2 rad
1' = 1 minuteofarc 60
1" = 1 secondofarc J6_0/
Selected Units Used inAstronomy
length 1 astronomicalunit = 1.50 X 10" n
1 light-year = 9.46 X 10'5m
1 angstrom = 10 10m
mass 1 solarmass = 1.99 X 1030kg W
power 1 solarluminosity = 3.90 X 1026
m
"This dreadand darkness ofthe mind cannot be
dispelled by thesunbeams, theshiningshafts ofday,
butonly by an understandingofthe outwardform
and innerworkings ofnature."
Lucretius
Susan M. Lea
San Francisco State University
John Robert Burke
San Francisco State University
^^P'
Brooks/Cole Publishing Company
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Physics : the nature ofthings/ Susan Lea, John Burke. Electricdisplacementvector ~
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ISBN 0-314-05273-9 student edition (alk. paper)
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1. Physics. I. Burke, John (John Robert) II. Title.
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To the special people in mylife:
myfather and mother, myhusband Michael and mydaughter Jennifer.
Thankyou.
Susan Lea
To my father,whose thirst for knowledgewas an inspiration.
John Burke
ABOUT
THE
AUTHORS
^, usan Lea is a professor ofPhysics and Astronomy at San Francisco State Univer-
^^L sity, where she has taught since 198] Born in Wales, she received her undergradu-
M .
M ate degree from Cambridge University, with 1st class honors in applied mathe-
^^^^^ matics and theoretical physics. She did her graduate work at the University of
California, Berkeley, receiving a Ph.D in Astrophysics. Sheworked extensivelywith datafrom
x-raysatellite missions, including Uhuru, HEAO 1 and the Einstein Observatory. Sheandher
husband own and operate a software company offering optical ray tracing software. She has
published extensively in the astronomical journals, but her first refereed paper (in an engi-
neeringjournal) was on the theory ofloudspeaker design! She began teaching physics at the
age of 16 (in high school), and hasn't stopped since.
Dr. Lea's interests includeflying (she holds aflight instructorcertificatewithairplaneand
instrument ratings), horse ridingand music.
m M
Professor ofPhysics at San Francisco State Universitysince 1972, Dr. Burkehas
\ B ^^r enjoyedsharinghisloveofsciencewithyoungpeopledecidingontheircareers.
m As a voracious young consumer ofscience fiction and serious studies ofspace
-^L. exploration, Dr. Burke's own path was set by visits to dad's job at then new
particle accelerators and by Fred Hoyle's popular astronomy books. "It was so cool to know
wecouldexplore atoms orpicture the Earth fourbillion years ago, meltedbymeteoritebom-
bardment, its core forming from liquid iron dribbling inward." Undergraduate work at Cal-
tech and graduate workin astrophysics at Harvard led to a research specialtyin physicsofthe
interstellar medium, with occasional forays into acoustics, economics, and relativity. It was
also at Harvard that Dr. Burke's interest in physics eduation bloomed. "I hadtheopportunity
to study teaching with outstanding masters of the craft. Concern for how people come to
understand, how they fit science into their lives, and how they learn to think with precision
have sinceguided all mywork."
Ofcourse, it's not all work. On occasion "J.R.B." can be caught taking in an earlymusic
concert, trekkingawilderness, climbingtheoddmountain, ortakinghisplaneintosomeout-
of-the-wayairport.
IV
PREFACE
To the Instructor
examples, and problems. In the first few chapters calculus is used
sparingly, mostly in optional sections, so that those students who
Otiuusr,baoRookmsatnitlweriistetrakoefntfherofimrsDteceRnteurruymANDat1uwrhao, atrwieodrktobpyerLsuucared-e abroeokj,usmtosrteartfianmgilicaarlictuyluiss awsilslumneodt.bAenoivnetrewrhleudlemefdo.lloLwatienrg Cinhatph-e
his readers by using logical arguments based on observation and
— ter 7 discussesthe useofintegration in physicsand presentsafive-
experience. This approach is still in style modern physicistsem- step plan for setting up integrals. Basic knowledge ofalgebra, ge-
ploy the same methods. Like Lucretius, both research physicists
and physicsstudentsstruggletounderstand "thenatureofthings." ometry, and trigonometry is assumed. Appendix I includes some
basic relations from these disciplines as a reminder and reference
for students.
Goals
This book can be used by students with widely varying levels
A primarygoal ofthis book is to help sciencestudentsdevelopthe oinfgaboirlietyx.clEuadcihngchtahpetDeirgsgtirnegssDeesetpheerbbaosxiecs,cotnhceeoppttsiofniraslt.MBaytihncTloupdi-c
kinds oflogical thinkingthat theywill need to understandphysics.
boxes, Optionalsections (markedwith an #),andtheAdvancedand
These skills are useful in physics and other disciplines aswell. Stu-
ChallengeProblems, the instructor can tailor the text to her or his
dents often find physics the most difficult ofthe sciences because,
own students. Instructor marginal notes (in blue) indicate which
even in the introductorycourses, it demands much morethanthe optional topics are used later in the book, and also explain the
memorization offacts.To studyphysicssuccessfully,studentsneed reason forsome ofourchoices oftopic and organization. Wehave
to learn to thinklike physicists. Studentsmust movebeyondbeing
— also given references for some ofour sources.
hunters and gatherers offormulae to solve problems they must
become, like physicists, creative problem solvers. In this book we
Organization
have tried to help students develop the logical reasoning and ana-
lytical skills that enable a physicist to practice his or her art. The order oftopics in the book is largely traditional, but is orga-
Citizens in a modern technological society need to be scien- nized to allow a large range ofsequencing options. For example,
tifically literate. That only a small, elite group of bright students introducing angular momentum ofa particle in Part II offers the
survives introductoryphysicsandgoeson tobecomeaerodynamic option offoregoing rigid body dynamics in favor ofa faster move
engineers or physics professors is no longer acceptable. We hope to the twentieth century. The chapter on oscillatorymotion could
to makephysicsaccessibletoallthosewhochoosetotakeaphysics be used any time after the discussion ofenergy (Chapter 8). We
course. We make it accessible not bywatering it down, butbygiv- have included optics in the section on wave motion, to stress the
ing students the tools they need to grab hold o—f the subject and unity of such wave phenomena as interference. However, Chap-
ma—keittheirown. Physicsisfascinatingandfun atleastwethink ters 16-18 on optics could easilybe covered after E&M ifdesired.
so and we have tried to convey some of our own enthusiasm Part V on thermodynamics is selfcontained and could be studied
for the subject. Examples such as the motion ofa "hot-dog" skier any time after basic mechanics. The first three sections ofChap-
(Example 3.5, Exercise 3.2) showthepowerofphysicsasatoolfor ter 34 (relativity) could be covered after Chapter 3, and Sec-
understanding the world and, at the same time, spark students' tion 34.4 could be introduced after Chapter 8. The chapters on
interest. modern physics tend to be more qualitative, because ofthe level
Intended for a course that requires calculus as a prerequisite
of mathematical sophistication required for a detailed treatment.
or co-requisite, this text uses calculus throughout, in derivations, They are designed to serve as the culmination ofa two- or three-
semester survey or as an impedance-matching introduction to a
1Lucretius based his book on earlier work by the Greek philosopher standard courseon modern physics. Thesechaptersemphasize the
Democritus. conservation principles developed in Part II.
Throughout the book we stress two major themes: conceptual The Solution Plans can also be valuable teachingtools, allow-
understanding and a consistent approach to problem solving. The ing you to identify precisely where students have difficulties. For
material in the book is divided into eight parts, each introducing example, using the plan in Chapter 5, we found that an astonish-
a unified body ofconcepts: Newtonian Mechanics; Conservation ingly large number ofstudents are convinced that they can't ana-
Laws; Continuous Systems; Oscillations and Waves; Thermody- lyze a system with strings unless they know the value ofthe ten-
namics; Electromagnetic Fields; Electrodynamics; and Twentieth sion before carrying out the algebra. Once these difficulties have
Century Physics. This division helps the students organize their been identified, it is much easiertoconfrontthem and, ultimately,
knowledge. The introduction toeachpartexplainsthethemetobe eliminate them.
covered and provides some historical perspective. We begin each The careful useofvectors is stressed throughout. In particular
chapter with a discussion ofthe opening photograph, frequently we introducevectorsas theprimarydescriptivetool in kinematics,
raising a question that we answer within the chapter. Just as each usinggeometricaladdition (Sections 1.4-1.6),andthensolveone-
chapter begins with a physical situation to introduce the concepts dimensional problems as a special case ofone-componentvectors
ofthe chapter, each topic within the chapter is introduced with a (Section 2.3). Not only does this approach stress the importance
conceptual discussion before the mathematics is presented. In this ofvectors from the beginning, but it makes the meaning ofsigns
wayweemphasizethatworkingwiththeconceptsisthefirstessen- in one-dimensional motion obvious. (An instructor's marginal
tial step in solving a problem. Then the mathematics is used to note on page 52 explains how this material can be presented in
complete the solution. Similarly, we place a great deal ofempha- other sequences.) In addition to boldface type, we have used the
sis on using diagrams to help conceptualize problems and plan "arrow-over" notation so that equations in the book will look the
theirsolution. Weencouragestudentsto usediagramsasgraphical sameasthe equationsyouwriteon theblackboard,orthestudents
tools to aid their understanding and to help make the transition write in their notes. We have avoided the use of "magic" minus
from a verbal presentation to a mathematical model. Unlike many signs (as in the spring force) that are not explicitly tied to a coor-
texts, we not only tell students to use diagrams, we always do it dinate choiceor stated sign convention.
ourselves. Beginningstudents often focus on finding"theanswer"with-
out first framing any expectation ofwhat the magnitude, units or
Problem Solving other characteristics oftheanswer mightbe. As scientists, instruc-
torsknowtheimportanceofestimationasaproblem-solvingstrat-
Two Interludes in the early parts ofthe text help lay the ground- egy. It can be difficult to integrate this strategyinto teaching,how-
work for a systematic approach to problem solving. In the first ever, especially ifstudents don't see it used regularly in their text.
interlude, following Chapter 3, we lay out our basic four-part Weintroducestudentstothesevaluableskillsbyusingback-of-the-
problem-solving strategy. The major stages ofeach problem sol—u- envelope calculations to estimate results, or to decide what is or is
tion MODEL SETUP SOLVE and ANALYZE not important in a given situation. Thesemethodsarealso usedto
, , ,
are identified and discussed at this point. Thesestepsare used and estimate the reasonableness ofan answerorto figureoutthebasic
labelled in everyexamplethroughoutthebook. Seeingthemethod physics behind a complicated event like a thunderstorm. The en-
at work in each example better enables students to apply a similar velope symbol ( ) alerts the students whenever we use these
approach in their own solutions. techniques in examples or discussions. Some problems show this
The second Interlude, following Chapter 7, shows students symbolto indicatethatthestudentsshouldusethesetechniquesin
how to set up problem solutions using integration. The method their solution, and that an exact answer is not expected.
involves five steps. The first foursteps area procedurefordescrib-
ing a physical process or system in terms ofdifferential elements Examples, Questions, and Problems
and transforming a sum over such elements to a standard mathe-
matical form. Only at the final step does the actual evaluation of Each chapter starts by emphasizing the basic concept, then devel-
an integral occur. This final step is the one that students learn in oping it through a carefully graded series of Examples. All Ex-
theircalculusclasses. Ineachexample requiringintegrationweuse amples consistently use the four-part problem-solving strategy
this method, with the steps clearlylabelled. presented in the first Interlude, and show the appropriate free-
Throughout the book we present Solution Plans. These are body diagram or other illustration at each step. While we have at-
problem-solving strategies that showthe logical steps necessary in tempted to keep the introductory examples straightforward, and
certain specific classes ofproblems. Each plan is explicitlylaid out to assure that they demonstrate a steady gradual increase in diffi-
in flow-diagram form. The method for analyzing dynamical sys- cultythroughout a chapter or part, twenty StudyProblems, spread
tems with Newton's laws (Chapter 5, p. 167) provides a good ex- throughout the book, emphasize the use of the problem-solving
ampleofa Solution Plan. A table in the appendixlists all theplans method in detail with interesting and sometimes intricate prob-
for easy reference. These Solution Plans will help the students de- lems. The inclusion of these problems should help to alleviate
velop the skills they need to solve problems in physics, and help the complaint that the "examples didn't prepare me to do the
them to go beyond that hunter-gatherer, "find the right equation problems."
and stuffin," stage. As students become more proficient theywill The text offers many opportunities for students to test their
be able to adapt these problem-solving strategies to their personal knowledge and theirabilityto use the material. Within eachchap-
style. ter, Exercises allow students to practice with ideas they have just
vi Preface
