科技英语.docx

科技英语.docx

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科技英语

Chapter1

Measurement

1-1Measuringthings

1.Physicsisbasedonmeasurement.

2.Aphysicalquantityisdefinedbysettingupastandardandassigningaunittoit.

3.Scientistsaroundthewordwillagreethatyourdefinitionis

（1）sensible

（2）practical（3）accessible

（4）invariable（5）reproducible（6）indestructible

1-2TheInternationalSystemofUnits

1.Metricsystem-SI

Franchname:

SystèmeInternationaled’unités

2.SEVEVfundamental（basebasic）SIunits

P.Q.

UNIT

ABBREVIATION

length

meter

m

mass

kilogram

kg

time

second

s

electriccurrent

ampere

A

temperature

kelvin

K

luminousintensity

candela

cd

amountofsubstance

mole

mol

Thesupplementaryunits

planeangle

radian

rad

solidangle

steradian

sr

3.ScientificnotationandSIprefixes

1-3ThreeBasicStandards

1.LENGTH

Themeteristhelengthofthepathtraveledbylightinvacuumduringatimeintervalof1/299,792,458ofasecond.

2.TIME

Onesecondisthetimeoccupiedby9,192,631,770vibrationsofthelight（ofaspecifiedwavelength）emittedbyacesium-133atom.

3.MASS

（1）aplatinum-iridiumcylinder

（2）asecondmassstandard

Itisthecarbon-12atomwhich,byinternationalagreement,hasbeenassignedamassof12unifiedatomicmassunits（abbr.U）.

1-4ChangingUnits

Chain-linkconversions

Chapter2

motioninastraightline

2-1Motion

1.Kinematicsanddynamics

2.Particle

Everysmallpartoftheobject（everyatomsay）movesinexactlythesameway.

2-2Speed,velocityandacceleration

1.Averagespeed,velocityandacceleration

2.Instantaneousspeed,velocityandacceleration

3.Speedisascalarandalwayspositive;velocityandaccelerationarevectorsandcanbepositiveornegative.

2-3Freefallingobjects

Whenafallingobjectisfreeofallrestraint（nofriction,airetc.）,andfallsundertheinfluenceofgravityalone,theobjectisinastateofFREEFALL,whichmeansfallinginavacuum,sothatthefrictionresistanceandbuoyanteffectoftheairdonotaffectthemotion.

2-4Thestructureofmatter

AllordinarymatterthatweencounterismadeofATOMSwhich,inturn,arecomposedofelectrons,protons,andneutrons.Theatomsofaparticularchemicalelementallhaveacertainnumber（theATOMICNUMBERZoftheelement）ofprotonsintheirnuclei.Anatomicnucleusalsohasacertainnumberofneutrons（theNEUTRONNUMBERN）,thesumofNandZbeingtheMASSNUMBERA.Thereareseveralpossiblemassnumbersforeachchemicalelements,eachonedesignatinganISOTOPEoftheelement.

Chapter3

vectors

3-1Vectorsandscalars

1.AvectorisaquantitythathasMAGNITUDEandDIRECTIONandthatfollowscertainrulesofcombination（translationproperty）.

2.AscalarisaquantitythathasONLYMAGNITUDE,requiresNOspecificationofdirection,andfollowstherulesofalgebra.

3-2Unitvector

1.Features

unitymagnitude,nodimensions,nounits

2.TheonlypurposetointroduceaunitvectoristospecifyaDIRECTION.

3-3Multiplyingvectors

1.Multiplyingavectorabyascalarc

Scalartimesvector

2.Thescalarproduct-dotproduct–isascalar

3.Thevectorproduct–crossproduct–isavector

Right-handRule

3-4Vectorsandphysicallaws

Anyphysicalsituationinvolvingvectorscanbedescribedusingseveralpossiblecoordinatesystems（referenceframes）.Weusuallychoosetheoneofthesethatsimplifiesourwork.However,therelationbetweenthevectorquantitiesdoesnotdependonourchoice.Thelawsofphysics,writteninvectorform,usesuchrelations.Wesaythatthelawsofphysicsareindependentofourchoiceofreferenceframe.

Chapter4

motioninaplane

4-1Threedimensionalcoordinatesystem

Inthreedimensions,aparticlecanbelocatedbyaVECTORr,extendingfromtheoriginofcoordinatesystemtotheparticleposition.

4-2Projectilemotionunderno-atmosphereconditions

weanalyzeprojectilemotion（oranyothermotionforwhichaccelerationisaconstant）byresolvingpositionr,velocityvandaccelerationaintoxandycomponents,treatingeachcomponentasanindependent,one-dimensionalmotion.

4-3Uniformcircularmotion

Inuniformcircularmotion,aparticlemoveswithconstantspeedvinacircleofradiusr.Thisisacceleratedmotionbecausethedirectionofthevelocityiscontinuouslychanging.Theaccelerationisalwaysdirectedtowardthecenterofthecircleandhasaconstantmagnitude.

4-4

Relativemotion

ThepositionofPasmeasuredbyAisequaltothepositionofPasmeasuredbyBplusthepositionofBasmeasuredbyA.

ThevelocityofPasmeasuredbyAisequaltothevelocityofPasmeasuredbyBplusthevelocityofBasmeasuredbyA.

Bothobservers,inreferenceAandB,willmeasurethesameaccelerationforthemovingparticle.

Chapter5

forceandmotion-I

5-1LimitationstoNewtonianmechanics

TherearesomeimportantproblemstowhichNewtonianmechanicsdoesnotgivecorrectanswers.Ifthespeedsoftheparticleinvolvedareanappreciablefractionofthespeedoflight.WemustreplaceNewtonianmechanicsbyEinstein’sspecialtheoryofrelativity.Forproblemsonthescaleofatomicstructure（forexample,themotionsofelectronswithinatoms）,wemustreplaceNewtonianmechanicsbyquantummechanics.WenowviewNewton’smechanicsasaspecialcaseofthesetwo,morecomprehensivetheories.Itisaveryimportantspecialcase,however,encompassingasitdoesthemotionsofobjectsthatrangeinsizefrommoleculestogalaxies.Withinthisbroadrangeitishighlyaccurate,asthesuccessfulmaneuveringofspaceprobesremindsus.

5-2Newton’slaws

1.Newton’sfirstlaw（thelawofinertia）

Considerabodyonwhichnonetforceacts.Ifthebodyisatrest,itwillremainatrest.Ifthebodyismovingwithaconstantvelocity,itwillcontinuetodoso.

Ifthenetforceactingonabodyiszero,itispossibletofindasetofreferenceframes（inertiareferenceframes,inwhichthelawsofNewton’smechanicsholds）inwhichthatbodyhasnoacceleration.

Thingsatresttendtostayatrest;thingsmovingtendtocontinuemoving.ThistendencyofthingstoresistchangesinmotionisINERTIA.

2.Newton’ssecondlaw

Theaccelerationofanobjectisdirectlyproportionaltothenetforceactingontheobject,isinthedirectionofthenetforce,andisinverselyproportionaltothemassoftheobject.

3.Newton’sthirdlaw

Youcannottouchwithoutbeingtouched（actionforceandreactionforce）

Wheneveroneobjectexertsaforceonasecondobject,thesecondobjectexertsanequalandoppositeforceonthefirst.

Anaction-reactionpairalwaysactsondifferentbodiessothattheycannotpossiblycanceleachother.

5-3Massandweight

Massisthequantity（scalar）ofmatterinamaterialobject.

Massisameasureoftheinertiaofamaterialobject,Themorematter,themoreinertia.

Weightistheforce（vector）uponanobjectduetogravity.

Massisanintrinsicpropertyofthebody,andmorefundamentalthanweight.

Measuringinstruments

Theequal-armbalanceandspringscale

Chapter6

forceandmotion-II

6-1Friction

Theforceoffrictionincludeskineticandstaticfrictionforces.

Thekineticfrictionalforce（associatedwithmotion）isusuallylessthanthemaximumvalueofthestaticfrictionalforce,whichactswhenthereisnomotion.

Thefrictionalforceisbasicallyanelectro-magneticforce.

6-2Uniformcircularmotion

Acentripetalforceisnotanewkindofforce.

6-3Theforcesofnature

1.Thegravitationalforce,2.Theelectromagneticforce,3.Theweakforce,4.Thestrongforce.

Chapter7

workandkineticenergy

7-1AwalkaroundNewtonianmechanics

Newtonianmechanics,grandasitsstructuremaybe,doesfailwhenweapplyittoparticlesmovingatspeedscomparabletothespeedoflight,yieldingtheretoEinstein’sspecialtheoryofrelativity.Italsofailswhenweapplyittomotionsofelectronsinatoms,yieldinginthatcasetoquantumphysics.Thelawofconservationofenergy,however,holdsinallthesedomains.ItisapeakevenhigherthenthepeakofNewtonianmechanics.

7-2Work

3.Motioninone-dimensionwithaconstantforce

Workisascalar.

Unit:

NewtonmeterNm;JouleJ

electron-volteV;kilowatthourkWh

4.Motioninone-dimensionwithavariableforce

theintegralofthefunctionF（x）betweenthelimitsxiandxf

5.Workdonebyaspring

Hooke’slaw:

Toagoodapproximationformanysprings,theforceF（x）exertedbythespringisproportionaltox,theextensionofthespring.

Theworkdonebythespringontheagentthatisstretchingorcompressingitis

.Theworkdoneonthespringbythatexternalagentisthenegativeofthisquantity.

derivativesandintegrals;slopeandareas

7-3Work-energytheorem

Thechangeintheenergyofaparticleisequaltothetotalworkdoneonthatparticlebyalltheforcesthatactonit（netforce）.

7-4Power

unit:

watt

7-5Referenceframe

Theprincipleofinvariance:

Thelawsofphysicsmusthavethesameforminallinertialreferenceframes.

Chapter8

theconservationofenergy

8-1Conservationlaws

Considerasystemofparticles,completelyisolatedfromoutsideinfluences.Astheparticlesmoveaboutandinteractwitheachother,thereisacertainpropertyofthesystemdoesnotchange.

8-2Potentialenergy

Potentialenergy（configurationenergy）isenergy“stored”inasystembecauseworkhasbeendoneagainstsomeconservativeforce.Theenergystoredinastretchedspringandtheenergystoredinanelevatedmassarecommonexamples.

8-3Conservativeandnonconservativeforces

Aforceisconservativeiftheworkitdoesonaparticlethatmovesthrougharoundtripiszero;otherwise,theforceisnonconservative.

Aforceisconservativeifthewo