chapter 5- equilibrium of a rigid body：5章刚体的平衡

《chapter 5- equilibrium of a rigid body：5章刚体的平衡》由会员上传分享，免费在线阅读，更多相关内容在应用文档-天天文库。

1、Chapter5-Equilibriumofarigidbody5.1Conditionsforrigid-bodyequilibriumPreviouslywefoundthatasystemofforcescanbereducedtoaforce-couplesystem.Whentheforceandcoupleareequaltozero,thebodyissaidtobeinequilibrium.Thenecessaryandsufficientconditionsfortheequilibriumofrigidbodyare:Incomponentform:Equilibr

2、iumintwodimensions5.2Free-bodydiagramsDrawingaFBD,steps1).Decidewhichbodytoanalyze.External2).Separatethisbodyfromeverythingelseandsketchthecontour,forces3).Drawallappliedforces(weight).4).Drawallreactions.5).Includeanynecessarydimensionsandcoordinateaxis.Ifyoudon'tknowadirectionassumeadirectiona

3、ndletthesignoftheanswertellyouifthedirectioniscorrectornot.Rules:1)Themagnitudeanddirectionofknownforcesshouldbeclearlyindicated(usuallyappliedforces)2)Indicatethedirectionoftheforceexertedonthebody,nottheforceexertedbythebody.Unknownforcesareusuallythereactions(constrainingforces).Reactionsaresu

4、pportsandconnectionsin2-D,pg.184-185.Thebest2waysIhavefoundtodeterminereactionsare:1)Removethesupportandseewhathappens12Lecture11.docFBDyxNmg2.Lookatasupportand"pull"onit.yxIfIpullontherod,itcan'tmoveinx,ydirection,butIcanmakeitrotateabout0.5.3Equationsofequilibriumyx3equations,3unknownsLet'slook

5、atatrussDQSCDA0B12Lecture11.docPQSFBDWAdditionalequationscouldbewritten.Doesnotprovideanynewinfo.Thisisnotanindependentequation.Youcanusetoreplaceoneoftheabove3.orHomework:Read:Problems5-12,19,23,27,30,3812Lecture11.doc1).GivenFind:ReactionsFBDSubstitutingintoRBy-equation:RAy=-1.5kN12Lecture11.do

6、c2).GivenFind:ReactionsatAFBD12Lecture11.doc3).Given:ThebarABweighs250poundsandallsurfacesaresmooth.Find:CabletensionandforcesatAandC.FBDSolvingtheabove3equationssimultaneously:RA=159.2lbsF=108.2lbsRC=141.2lbs12Lecture11.doc4).Given:Theloadingcarweightis5500lbs.anditsCGisatpointG.Find:tensioninca

7、bleandreactionsatwheels.FBDTofind,summomentsaboutAtoeliminateTandR.Tofind,summomentsaboutBtoeliminateTand12Lecture11.docTofindT:Check:12Lecture11.doc5).Given:ThetensioninDFis150kNFind:DeterminethereactionsatE(Pt.Eisfix