Springs&Strings

《Springs&Strings》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、Springs&StringsSpringsSpringForceAstretchedorcompressedspringexertsoneofthemostcommoncontactforces.Aspringcaneitherpush(whencompressed)orpull(whenstretched).Ineithercase,thetailofthevectorforceisattachedtothecontactpoint.Thereisnospecialsymbolforthespringforce,butwecanuseFsp.H

2、ooke’slawforspringsstatesthattheforceincreaseslinearlywiththeamountthespringisstretchedorcompressed:kspringconstantunitsN/mHooke’sLawSpringsHooke’slawforspringsstatesthattheforceincreaseslinearlywiththeamountthespringisstretchedorcompressed.Theforceisnegativebecauseitalwaysopp

3、osesthecompressionorextensionofthespring.Hooke’sLawSprings27••IPTheequilibriumlengthofacertainspringwithaforceconstantofk=250N/mis0.18m.(a)Whatforceisrequiredtostretchthisspringtotwiceitsequilibriumlength?(b)Istheforcerequiredtocompressthespringtohalfitslengththesameasinpart(a

4、)?Explain.0.18mF=-kxx=0.18mF=-(250N/m)(0.18m)F=-45N(a)(b)x=-0.09mF=-(250N/m)(-0.09m)F=22.5NThetensiontransmittedbyastring,rope,cable,etc.istheforceexertedbythestringateitherendandalongitslength.TensionThetensioninarealropewillvaryalongitslength,duetotheweightoftherope.Wewillas

5、sumethatallropes,strings,wires,etc.aremassless.So…T1=T2=T3TensionTensionACTWhatisthereadinginNoneachthetwospringscalesshownabove?9.8NIdealpulleyssimplychangethedirectionofthetension.Thereisnofrictioninthepulleyandthepulleysaremassless.Pulleys&TensionWhenforcesareexertedonconne

6、ctedobjects,theiraccelerationsarethesame.Inthesituationbelow,ifweknowtheforceandthemasses,wecanfindtheaccelerationandthetensionTension–ConnectedObjectsInadditiontothemotionoftheentiresystem,wecantreateachboxasaseparatesystem.Usetheentiresystemtofindtheaccelerationandthenuseone

7、oftheboxestofindthetension.Ifthereisapulley,itiseasiesttohavethecoordinatesystemfollowthestring.Tension–ConnectedObjects42.•••Twobucketsofsandhangfromoppositeendsofaropethatpassesoverapulley.Onebucketisfullandweighs110N;theotherisonlypartlyfilledandweighs63N.(a)Initially,youho

8、ldontothelighterbuckettokeepitfrommoving.Whatisthetensioninth