In praise of simple physics: the science and mathematics behind everyday questions

269 Pages·2017·3.909 MB·English

by  Nahin, Paul J

In Praise of
Simple Physics
OliverHeaviside(1988,2002)
TimeMachines(1993,1999)
TheScienceofRadio(1996,2001)
AnImaginaryTale(1998,2007,2010)
DuellingIdiots(2000,2002)
WhenLeastIsBest(2004,2007)
Dr.Euler’sFabulousFormula(2006,2011)
ChasesandEscapes(2007,2012)
DigitalDice(2008,2013)
Mrs.Perkins’sElectricQuilt(2009)
TimeTravel(1997,2011)
Number-Crunching(2011)
TheLogicianandtheEngineer(2013)
WillYouBeAliveTenYearsfromNow?(2014)
HolySci-Fi!(2014)
InsideInterestingIntegrals(2015)

Copyright(cid:1)c 2016byPrincetonUniversityPress
PublishedbyPrincetonUniversityPress,41WilliamStreet,
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IntheUnitedKingdom:PrincetonUniversityPress,
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JacketillustrationbyAnneKaretnikov
AllRightsReserved
Figure14.1onpage116isfromDarknessatNight:ARiddleoftheUniverseby
EdwardHarrison,Copyright(cid:1)c 1987byEdwardHarrison;bypermission
fromHarvardUniversityPress.
LibraryofCongressCataloging-in-PublicationData
Nahin,PaulJ.,author.
Inpraiseofsimplephysics:thescienceandmathematicsbehind
everydayquestions/PaulJ.Nahin.
pagescm
Includesbibliographicalreferencesandindex.
ISBN978-0-691-16693-3(hardcover:alk.paper)—
ISBN0-691-16693-5(hardcover:alk.paper) 1.Physics.
2.Mathematicalphysics. I.Title.
QC21.3.N342016
530—dc23 2015031463
BritishLibraryCataloging-in-PublicationDataisavailable
ThisbookhasbeencomposedinITCNewBaskerville
Printedonacid-freepaper.∞
TypesetbyNovaTechsetPvtLtd,Bangalore,India
PrintedintheUnitedStatesofAmerica
13579108642
For Patricia Ann

Contents
ForewordbyT.M.Helliwell ix
PrefacewithChallengeProblems xi
1
How’sYourMath? 1
2
TheTraffic-LightDilemma 20
3
EnergyfromMovingAir 25
4
DragstersandSpaceStationPhysics 32
5
Merry-Go-RoundPhysicsandtheTides 42
6
EnergyfromMovingWater 51
7
VectorsandBadHairDays 63
8
AnIlluminatingProblem 67
9
HowtoMeasureDepthwithaStopwatch 74
10
DoingthePrefaceProblems 79
viii CONTENTS
11
ThePhysicsofStackingBooks 92
12
CommunicationSatellitePhysics 103
13
WalkingaLadderUpright 110
14
WhyIstheSkyDarkatNight? 115
15
HowSomeThingsFloat(orDon’t) 126
16
AReciprocatingProblem 141
17
HowtoCatchaBaseball(orNot) 146
18
TossingBallsandShootingBulletsUphill 153
19
RapidTravelinaGreatCircleTransitTube 163
20
HurtlingYourBodythroughSpace 177
21
ThePathofaPunt 194
22
EasyWaystoMeasureGravityinYourGarage 200
23
Epilogue
Newton’sGravityCalculationMistake 218
Postscript 227
Acknowledgments 237
Index 239
Foreword
Physics is a glorious brew of diverse ingredients. No single approach
issufficientwhengrapplingwithNature.Experimentandobservation
areessential,ofcourse,butso,too,areconcepts,pictures,imagination,
mathematics, and physical intuition, topped off with logical consis-
tency. We are explorers in a maze with mysteries at every turn—not
forthefaintofheart!
Learningphysicsandteachingphysics(twosidesofthesamecoin)are,
likewise, all over the map. There are laboratories, lectures, problem
sessions, computer calculations, and books—any approach that can
help us understand. And books themselves take different approaches.
Someare“top-down,’’startingwithphysicallawsandthendeveloping
examples and applications. Others are historically based, developing
physics as the author imagines it was invented or might have been
invented if real history were not so full of diversions and blind alleys.
Yetotherbooksare“conceptually’’based,avoidingallmathematicslike
theplague.Andstillothersarepackedwithmathematicalanalysisbut
are thin on concepts, illustrations, and applications. Each approach
hasmerit.
InInPraiseofSimplePhysics,PaulNahintakesadifferent,refreshing
slicethroughthesubject.Heshowsussomereallyinterestingexamples
of applying simple physical principles to a variety of special cases,
questions,andpuzzles.
There are a myriad of topics here: we learn about wringing more
of our energy from renewable sources in the chapters “Energy from
Moving Air’’ and “Energy from Moving Water.’’ There is the futuristic
chapter,“RapidTravelinaGreatCircleTransitTube.’’Wefindouthow