newtons慣性大小只與質(zhì)量有關(guān)

NEWTON’SLAWSOFMOTION1SATIIphysicstestWhatis

force？？？3Newton’sFirstLawNewton’sFirstLawsaysthatobjectsinmotionwillremaininmotionunlessacteduponbyanexternalforce.Inertia4Inertia慣性大小只與質(zhì)量有關(guān)！慣性是保持物質(zhì)原有運(yùn)動狀態(tài)的屬性！5Newton’sSecondLawNetforceonanobjectcausesittoaccelerate.合外力與加速度大小成正比，方向相同靜止、勻速直線運(yùn)動變速運(yùn)動Fnet=0Fnet≠064m/s2VconstantFrictionnotnegligibleIfF=30NWhatistheacceleration?WhenF=70Nm=8kg5m/s27Newton’sThirdLawAction—reactionprinciple作用力與反作用力，成對出現(xiàn)，方向相反，大小相同8FrictionforceNormalforceTensionWeightfk=μkFnfs≤μsFnKineticStaticFreeBodyDiagrams：9Ifa20Nforceduewestcreatesanaccelerationof3m/s2,whatistheaccelerationifthemassoftheobjectisdoubled.1.5ms-2inthewestdirectionFindtheaccelerationandthetensioninthestringsUseg=-10m/s2AB6ms-2intheeastdirectionAB6ms-2inthesouthdirectionT=12N101.確定研究對象2.進(jìn)行受力分析3.矢量分解與求和4.(根據(jù)合力確定加速度)有關(guān)力與運(yùn)動的題目a=2gTmWFnT=?11θ1=30°,θ2=45°,m1=20kg,m2=?Fn1=m1gcos30°T=m1gsin30°T=m2gsin45°Fn2=m2gcos45°T=100NFn2=100Nm2=14.1kg12Findthetensions(T1andT2)andtheaccelerationofeachmasswhenaforceFisappliedtomassm1asshowninthediagrambelow.Assumethereisnofriction.Expressyouranswerintermsofm1,m2,m3,andF.對于同速系統(tǒng)，可以使用整體法13Amanwhohasamassof70kgstandsonthescaleinsidetheelevator.Findthescalereadingforthefollowingconditions.(g=10m/s2):(a.)Theelevatorisatrest.(b.)Theelevatorismovingupwithaconstantaccelerationof2m/s2.(c.)Theelevatorismovingdownwithaconstantaccelerationof2m/s2.(d.)Theelevatorismovingupwithconstantvelocity.(e.)Theelevatorcableiscut.|Fnet|=|mg-N|a70kgb84kgc56kgd70kge0kg14Frictionforce15A3kgblockisplacedontopofa10kgblockasshowninthefigurebelow.Thecoefficientofstaticfrictionbetweenbothblocksis0.5.Whatisthemaximumaccelerationthatthesystemcanhavewithouttoppling?FindthemaximumforceFthatcanbeappliedtothe10kgmass.(Assumethatthereisnofrictionbetweenthe10kgblockandthesurface.)Useg=10m/s2m1m2N2=m2gfs=m2afs=μsN2a=5m/s2N2+m1g=N1F-fs=m1aF=65NF=(m1+m2)a16g=9.8m/s217△y=2.4m；△x=1.8m；d=0.95m；mball