PhysicsWord格式文档下载.docx

PhysicsWord格式文档下载.docx

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inpointform

Displayofresults:

-table-graph

Results:

Errorsintheexperimentandwaystoimprovetogetaccurateresults:

PLO-Equationofmotion-uniformingacceleratedobject.

1）Vf=Vo+at

2）a=（Vf-Vo）/t

3）d=Vot+1/2×

at2

4）d=（Vf+Vo）/2×

t

5）Vf2=Vo2+2ad

Vf=finalvelocitym/sa=accelerationm/s2t=times

Vo=initialvelocitym/sd=displacement

PLO-Definitioninmotionandgraph

PLO-Projectiles

-projectilesareobjectswhicharefiredintotheair

-theirmotionobeyskinematicequationscompletelyifweignoreairresistance

-objectslaunchedwithahorizontalvelocityanddroppedformthesameheightwillalwaysstrikethegroundatthesametime.

-thetimeprojectilespendsintheairdependsuponitsinitialvelocityandverticalaccelerationonly.

Thehorizontal:

dx=Vot+1/2×

Thevertical:

dy=-1/2×

gt2

Dynamics

Differentbetweenkinematicanddynamics:

kinematicsdescribehowanobjectmoves;

dynamicsdescribewhyitmoves.

Force:

pushorpullexertedbyanobjectontheother.

Unitofforce:

Newton（N）1Newton=1kgm/s2

Typesofforces:

-frictionalforce（necessaryevil）

-gravitationalfore（existeverywhere）

-electricforce

-Magneticforce

-airresistance

-centrifugalforce

-centripetalforce

-normalforce（FN）:

actsperpendiculartothesurfaceonwhichtheobjectisplaced.

PLO-Newton'

slawofmotion:

Newton'

sfirstlaw（lawofinertia）

Whennoexternal,unbalancedforceactsonanobjects,itsvelocityremainconstant.

Ifnonetforceactsonanobject,itmaintainsitsstateofrestoritsconstantspeedinastraightline.

ssecondlaw:

Whenanexternal,unbalancedforceactsonanobject,theobjectaccelerates.Theaccelerationsisinthesamedirectionasthenetforceactingontheobject.

Theaccelerationvariesdirectlywiththenetforceapplied.

Theaccelerationvariesinverselywiththemassoftheobject.

Fnet=ma

sthirdlaw:

Foreveryactionthereisanequalandoppositereaction.

Actionandreactionalwaysoccurinpairs.

F1=-F2

slawofuniversalgravitation

Statethe:

a）thegravitationalforceisdirectlyproportionaltotheproductoftheirmasses:

Fg∝m1m2

b）Thegravitationalforceisinverselyproportionaltothesquareofthedistancebetweenthecentreoftheobjects.

Fg∝1/r2

Fg∝m1m2/r2

Fg=Gm1m2/r2

G=universalgravitationalconstant=×

10-11kg2→measuredbyCavemdishusingatorsionbalance

*massoftheearth=×

1024kg

Radiusoftheearth=×

106m

TheFrictionalforce:

Actsintheoppositedirectiontothemovementoftheobject.It'

srepresentedbyFf.

Thefrictionalforcedependson:

I）thenormalforce

II）thenatureofthesurface→coefficientoffriction→denotedbyμ（mu）

Ff=μFN

Energy

Elastic--abletostretchandreturntoitsoriginalsizeandshape

Elasticpotentialenergy--energypossessedbyanelasticobject.

Extension--extendedlength-originallength

Conservation--momentumdoesn'

tchange

Momentum--p=mv

Mechanicalenergy--Theenergyacquiredbytheobjectsuponwhichworkisdoneisknownasmechanicalsumofand

Energy--thecapacitytodowork

Potentialenergy--（storedenergy）=mgh

Kineticenergy--energypossessedbyamovingobject.=1/2（mv2）

Work--W=F×

d

Power--istherateatwhichworkisdoneorenergytransformed.（workdone）/（time）&

（energychanged）/（time）

Efficiency=（workoutput）/（workinput）×

100%

Workinput:

worksuppliedintothesystem

Workoutput:

usefulworkdone

Conservationofenergy:

Lawofconservationofenergy--energycaneitherbecreatedordestroyedbutonlytransformedfromaformtoanother.

Hooke'

slaw:

Theforceappliedisdirectlyproportionaltotheextension.

F=kx

F=forceapplied,x=extension;

k=forceconstant

*breakingpoint:

pointtowhichtheobjectexceedsitselasticlimit.

Momentum:

-conceptofmomentum

-Impulseandmomentum

-Collisionsandexplosions

-Elasticandinelasticcollision

Ft=p=m△v

Conservationofmomentum:

-notchangingconservedduringcollisions.

-"

headon"

InlinearInteraction:

1）elastic--objectcollideandmoveawayfromeachother

Beforecollision:

Totalmomentum=m1v1+m2v2

Aftercollision:

Totalmomentum=m1v1'

+m2v2'

2）Inelastic--objectscollide,sticktogetherandtravelatacommonvelocity.

Totalmomentum=（m1+m2）V'

Lawofconservationofmomentum:

totalmomentumbeforecollision=totalmomentumaftercollision

Mechanicalenergy

Mechanicalenergycanbeeitherkineticenergyorpotentialenergy:

Totalmechanicalenergy=potentialenergy+kineticenergy

LossinPE=gaininKE→lawofconservationofmechanicalenergy

ME=mgh+1/2（mv2）

power

Poweristherateatwhichworkisdoneorenergytransformed.

Power=（workdone）/（time）&

（energychanged）/（time）（J/s）

Power=Force×

velocityP=FV

SIunitofpowerisWatt（W）

P=I2RP=V2/RP=IV

Work

A.Energyisdefinedastheabilitytodowork.

B.Work=force×

displacement

C.Workismeasuredinwhichisalsocalledajoule（J）

D.Althoughworkisaproductoftwovectorquantities,itisascalarquantity.

E.Whentheforceisnotinthesamedirectionasthedisplacement,mustusethecomponentoftheforcethatisinthedirectionofthedisplacement.

PLO-waves:

characteristics

Vocabulary:

Pulse-asingledisturbancemovingthroughamediumfromonelocationtoanotherlocation.

Wave-asinglepulsewithacrestandatrough.

Crest-upperpartofthewave.

Trough-lowerportionofthewave

Wavemotion-seriesofwaves

Rarefactions-airparticlesarefarapart

Compression-regionwheretheairparticlearecloser

Medium-thesubstanceormaterialwhichcarriesthewave.（waterairsolids）

Transversewave-（lightwater）Directionofwavemotionisverticaltotheparticlemotion

Longitudinalwave-（soundwave）directionofwavemotionisinlinewiththedisplacementoftheparticles.

Progressivewave-wavethatcontinues.

Frequency-Thenumberofcompletewavesformedinasecond.MeasuredinHertz（Hz）.

Amplitude-Themaximumdisplacementofthewavefromthemeanposition.

Wavelength-thedistancetravelledbyacompleteinmetreslambda（λ）

Simpleharmonicmotion-motionthatmakecompletecyclesoveraperiodoftime.

Vibration-continuousmovementofparticles.

Slinky-

Transverseprogressivewave-Thedirectionofwavemotionisperpendiculartothedisplacementoftheparticles.

Awavetransportonlyenergyandnottheparticles-energytransportphenomenon

Sinewave-sinusoidalwave.

Timeperiod-timetakestomakeonecompletewave,oscillation.F=1/TT=1/f=1/hertz=second

Speedofsound-350m/s

Speedoflight-3×

10^5km/s

Mechanicalwave-wavethatrequireamediumtopassthrough.（ex:

sound,water）

Universalwaveequation-velocity（orspeed）=frequency×

wavelength.V=fλ

PLO-propertiesofwaves.

1）Reflection

Lightwaves:

reflectionisbouncingofwaveswhentheyhitareflectingsurfacewaveswhentheyhitareflectingsurface.

Lawofreflection:

-Theangleofincidenceisequaltotheangleofreflection∠i＝∠r

-theincidentray,reflectedrayandthenormallieonthesameplane.

Waterwaves:

Reflectlikelightwaves.Refractwhentheytravelfromdeeptoshallowregion.

Rippletank:

Speedofthewavesdecreaseswavelengthdecreasesfrequencyremainsunchanged.

Soundwaves:

reflectwhentheyhitobjects.

2）Refraction

Refractionmeansbendingwavesreflectwhentheytravelfromonemediumtotheother.

-thespeedoflightincreasedwhenitgoesintothelessdensemedium.（anglebecomebigger）

-thespeedoflightdepressedwhenitgoesintothemoredensemedium.（anglebecomesmaller）

Absoluterefractiveindex=（speedoflightinvacuum）/（speedoflightinmedium）n=C/V

Relativerefractiveindex:

Iflighttravelsfromairtoglasswetalkaboutrelativerefractiveindex.

Sini/Sinr=refractiveindex

Machnumber-theratioofthespeedofanobjecttothespeedofsound.

Sonicboom-thegreatsoundhappenedwhentheairplaneflyinahighspeedacrossthecompressedairinfront.

Decibel

Reverberation

Sonar

Radar:

PLO-propertiesofwaves:

Diffraction:

wavesbecomecircularwhentheyenteranarroworwideopening.

Narrowopening:

（greaterthewavelength,greaterthediffraction）

Wideopening:

Curvedonlyattheedges.

Interference:

-ConstructiveInterference

DestructiveInterference:

Theytendtocancelout.

Dopplereffect:

Thefrequencyofasourceincreasseswhenitapproachesthereceiver.

Polarisation:

Changingthevibrationalmodesofelectromagneticradiation.

PLO-Images

-Inopticalinstrumentstheimagesareformedwhenlenses（or）mirrorsareused.

-Theimagethatisformedonascreeniscalledarealimage.

-Theimagethatisnotformedonascreeniscalledavirtualimage.

Characteristicsofimage:

-real

-inverted

-smallerthantheobject

-inPhysicsthecharacteristicsoftheimagearestatedintermsof