定义整理

1.speed=distance/timetaken2.velocity=displacement/timetaken

NAME:

3.displacement:distancemovedbyanobjectinaparticulardirection4.scalar:hasonlymagnitude5.vector:hasmagnitudeanddirection6.acceleration:therateofchangeofvelocity7.mass:propertyofabodyresistingchangesinmotion8.weight:forceduetogravitationalforce

9.centreofgravity:thepointwhereallthepointisconsidered.

10.Newton’sfirstlaw:Anobjectwillremainatrestortravellingatconstantvelocityinastraightlineunlessitisactedonbyaresultantforce.

11.Newton’ssecondlaw:Forabodyofconstantmass,itsaccelerationisdirectlyproportionaltotheforceappliedtoit.

12.Newton’sthirdlaw:whentwobodiesinteract,theforcestheyexertoneachotherareequalinmagnitudeandoppositeindirection.

13.moment:force×perpendiculardistanceofthepivotfromthelineofactionoftheforce.

14.couple:force×distancebetweentwoforces

15.principleofconservationofmoment:Foranyobjectthatisequilibrium,thesumoftheclockwisemomentaboutanypointprovided

bytheforcesactingontheobjectequalsthesumoftheanticlockwisemomentsaboutthatsamepoint.16.equilibrium:resultantforce=0

resultantmoment=0

17.workdone:productofforceanddistancemovedinthedirectionoftheforce

18.gravitationalpotentialenergy(g.p.e.):theenergytodoworkofamassthatithasstoredduetoitspositioninagravitationalfield.

19.kineticenergy(k.e.):energytodoworkofanobjecthasduetoitsvelocity.

20.conservationofenergy:Energycannotbecreatedordestroyed.Itcanonlybeconvertedfromonetoanother.

21.momentum:theproductofitsmassanditsvelocity

22.principleofconservationofmomentum:Foraclosedsystem,thetotalmomentumbeforethecollisionequalsthetotalmomentumafterthecollision.

23.force:therateofchangeofmomentum.

24.perfectlyelasticcollision:relativespeedofapproach=relativespeedofseparation.

25.Density:massperunitvolume26.Pressure:forceperunitarea

27.Hooke’slaw:AmaterialsobeysHooke'slawiftheextensionproducedinitisproportionaltotheappliedforce

28.Stress:forceperunitarea

29.Strain:extensionperunitoriginallength30.Youngmodulus:stress/strain

31.Elasticdeformation:Materialreturnstoitsoriginalshapewhenforcesareremoved

32.Plasticdeformation:MaterialdoesNOTreturntoitsoriginalshapewhenforcesareremoved

33.Electricfields:Anelectricfieldisaregioninwhichchargedbodiesexperienceaforce.

34.electricfieldstrength:Theelectricfieldstrengthatapointelectricforceperunitthatpoint.

35.Electriccurrent:istherateofflowofelectricchargepastapoint36.Coulomb:isthechargewhichflowspastapointinacircuitinatimeof1swhenthecurrentis1A

37.Potentialdifference:energyisconvertedfromelectricaltootherformsperunitcharge

38.Electromotiveforce:energyisconvertedfromotherformstoelectricalperunitcharge

39.Resistance:potentialdifference/current40.Ohm:volt/ampere

41.Power:workdone/timetaken

isthe

chargeexertedonastationarypositivechargeat

42.Kirchhoff'sfirstlaw:Thesumofthecurrentsenteringanypointinacircuitisequaltothesumofthecurrentleavingthatsamepoint.43.Kirchhoff'ssecondlaw:thesumofe.m.f.saroundanyloopisequaltothesumofp.d.saroundtheloop.

44.Ohm’slaw:AconductorobeysOhm'slawifthecurrentinitisdirectlyproportionaltothepotentialdifferenceacrossitsends.

45.Amplitude:isthemaximumdisplacementofthemediumfromitsequilibriumposition.

46.Wavelength:istheminimumdistancebetweentwopointswhichareinphase

47.Frequency:isthenumberofcompleteoscillationsinonesecond48.Period:isthetimetakenforonecompleteoscillation.

49.Wavespeed:isthedistancetraveledbyawaveformperunittime.50.Longitudinal:vibrationsoftheparticlesareparalleltothewavedirection

51.Transverse:vibrationsoftheparticlesareperpendiculartothewavedirection

52.Dopplereffect.theobservedfrequencyisdifferenttotheemittedfrequencywhenthereisrelativemotionbetweenthesourceandobserver.53.Superpositionofwaves:whentwoormorewavesatapoint,theresultantdisplacementisthealgebraicsumofthedisplacementsoftheindividualwaves

.node:equilibriumposition55.antinode:maximumdisplacement

56.DifferencebetweenprogressivewavesandstationarywavesProgressivewaves

progressivewavestransferenergy.

Stationarywaves

stationarywavesdoesnottransferenergy

Allparticleshavedifferentphases

Allthepointsbetweenadjacentnodesareinphase

AllthepointsalongthewavehaveTheamplitudeofdifferentpointssameamplitude.

varyfromamaximumtozero.

57.Interference:isthesuperpositionoftwoormorewavesinsimilardirectiontogivearesultantwavewhoseamplitudeisgivenbytheprincipleof

superposition.

58.Coherent:identicalwavelengthsandfrequencyconstantphasedifference

59.Diffraction:Thespreadingoutofwavewhenwavespassthroughagap

60.Isotopes:arenucleiofthesameelementwithdifferentnumbersofneutronsbutthesamenumberofprotons.

61.Hadrons['hædrɒn]:suchasprotonsandneutrons.Theseareallparticlesthatareactedbythestrongnuclearforce.

62.Leptons['leptɒn]:suchaselectrons.Theseareparticlesthatarenot

actedbythestrongnuclearforce.