Alevel物理这些概念不会，拿A就悬了...

　　Alevel物理这些概念不会，拿A就悬了...今天我们来总结一下Moment、Material和Wave这三部分需要掌握的重要概念吧！

　　Moment

　　1

　　Moment– Forcemultipliedbyperpendiculardistancebetweenforceandthe pivot

　　2

　　Principleofmoments– Statesthatforanobjecttobeinequilibriumthesun oftheanticlockwisemomentsequals thesumoftheanticlockwisemoments (noturningmoment)

　　3

　　AnObjectisinequilibriumif:

　　Sumofanticlockwisemoments=sumofclockwisemoments

　　Allverticalforcescancelandallhorizontalforcescancel

　　4

　　ACouple– Apairofoppositeandequalforcesseparatedbydistanced, actingaboutpointp,theturningeffectatpointpisequaltooneofForces multipliesbytheperpendiculardistancebetweentheforces

　　5

　　Centreofmass– Whereallofanobjectsmassappearstoactaboutand momentscancel

　　Materials

　　6

　　ANewton– Forcerequiredtoaccelerate1kgby1ms-2

　　7

　　 AJoule– Workdone1Nthroughadistanceof1mindirectionofforce

　　8

　　Lawofconservationofenergy– energyisnevercreatedordestroyedjust convertedbetweendifferenttypes

　　9

　　Hooke’sLaw– Theextensionofaspringisproportionaltotheforceapplied toitaslongasthelimitofproportionalityisnotexceeded

　　10

　　Stress– Forceperunitarea ? Strain– Ratioofextensiontooriginallength

　　11

　　Young’sModulus– Stiffnessconstantofamaterial

　　Waves

　　12

　　AlongitudinalWave– apropagatingwavewithoscillationsinthesame directionaspropagation/energytransfer

　　13

　　Atransversewave– Apropagatingwavewithoscillationsperpendicularto thedirectionofpropagation

　　14

　　Transversewavescanbepolarizedbutlongitudinalwavescannot

　　15

　　Stationarywave– Formedwhen2wavesofsimilarfrequencytravellingin oppositedirectionsinterfereandtheresultantwaveisthevectorsumofeach wavesdisplacementsatthatpointbytheprincipleofsuperposition

　　16

　　Diffraction– Spreadingoutofawavewhenpassedthroughaslitofaround anobstacle

　　17

　　CoherentSources– Samefrequencyandconstantphaserelationship

　　18

　　ConstructiveInterferenceoccurs– 2wavesintersectandinterferethrough principleofsuperpositionandtheresultantdisplacement.

　　Thevectorsumofthe2wavesdisplacementatthatpointandthephase differencebetweenthe2wavesatthatpointisawholenumberofwavelengths (destructivewhen180degreesphasedifference– halfnumberofwavelengths)

　　19

　　Differencesbetweensingleanddoubleslitdiffraction–

　　Single– Widecentralmaxima2xwidthofothersandreductioninintensity goingaway

　　Double– Sameintensitysamewidthgoingout