H2 Physics Definitions

PhysicsDefinitions Topic Term Definition Measurements Systematicerror Systematicerrorscausemeasurementstobeconsistentlyhigher/lowerthanthetruevaluebyafixedextent. Accuracy Thedegreeofclosenessofameasuredvaluetothetruevalueofaquantity.Anexperimentthathassmallsystematicerrorsissaidtohavehighaccuracy. Randomerrors Randomerrorscausemeasurementstobescatteredaboutameanvalue. Precision Thedegreeofclosenessbetweenrepeatedmeasuredvalues.Anexperimentwithsmallrandomerrorsissaidtohavehighprecision. Kinematics Viscousdragforce Theforcewhichopposestherelativemotionofabodymovingthroughafluid. Distancevsdisp Distanceisthetotallengthoftheactualpathtravelled.Displacementisthestraightlinedistance. Forces Hooke’slaw Statesthatwithinthelimitofproportionality,theextensionproducedinamaterialisdirectlyproportionaltotheloadapplied.(F=kx) Pressure Isforceperunitarea,whereforceisactingperpendiculartoarea.(P=F/A) Density Ismassperunitvolumeofsubstance. Upthrust Isthenetupwardforceexertedbyafluidonabodyfullyorpartiallysubmergedinthefluid,duetoadifferenceinpressure. Principleofflotation Forabodyfloatinginafluid,theweightofthefluiddisplacedbythebodyisequaltotheweightofthebody. TorqueMOMENT Torque:turningeffectofacoupleMoment:Theproductofthemagnitudeoftheforceandtheperpendiculardistanceofthelineofactionoftheforcetothepivot.(M=Fd)

Couple Apairofforceswhichareequalinmagnitudebutoppositeindirection,andwhoselinesofactiondonotcoincide(parallel).Producerotationonly. Principleofmoments Forabodyinrotationalequilibrium,thesumofallclockwisemomentsaboutanypointisequaltothesumoftheanticlockwisemomentsaboutthatsamepoint. Rotationalequilibrium Thenetmomentonthebodyaboutanypointiszero. Translationalequilibrium Thenetforceonthebodyiszero. Dynamics centreofgravity pointatwhichthewholeweightofbodyappearstoact N1L Anobjectatrestwillremainatrest.Anobjectinmotionwillremaininmotionatconstantvelocityinastraightlineunlessacteduponbyaresultantexternalforce Inertia Reluctanceofastationarybodytostartmoving,orreluctanceofamovingbodytochangeitsmotion/Reluctanceofabodytochangeitsstateofmotion/Propertyofabodytostayinastateofrestorstayinmotionatconstantvelocityinastraightline.Massisameasureofinertiainabodytochangeinvelocity. N2L ● (MAG)rateofchangeoflinearmomentumofbodyisdirectlyproportionaltonetexternalforceexertedonit● (DIR)changeinmomentumandnetexternalforceareinthesamedirection VSstatetherelationbetweenforceandmomentum:forceisequaltotherateofchangeofmomentum.(SIunitscauseproportionalityconstanttobe=1.) N3L IfbodyAexertsaforceonbodyB,thenbodyBwillexertaforceequalandoppositeandofthesametypetobodyA. linearmomentum (p=mv)productofmassandvelocityAnditisinthedirectionofthevelocity

POCOM Totallinearmomentumofasystemofinteractingbodiesremainsconstantprovidedthereisnoresultantexternalforceactingonit. Impulse productofaverageforceexertedonbodyandtimeintervaloverwhichforceisapplied(Δ p=Ft) head-oncollision Velocitiesbeforeandafterthecollisionarealongthelinejoiningthe2centresofmass. perfectlyinelasticcollision coll