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Revision Paper IA Structures Free Body Diagrams Fricti Revision Paper IA Structures Free Body Diagrams Fricti

Revision Paper IA Structures Free Body Diagrams Fricti - PDF document

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Uploaded On 2015-04-28

Revision Paper IA Structures Free Body Diagrams Fricti - PPT Presentation

You can easily adjust the position of the lamp and it will always remain in the position you left it in Its working principle is very simple but very clever at the same time And you can now calculate how it works The original Anglepoise lamp was inv ID: 56215

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(a)Original1932AnglepoisedesignbyGeorgeCarwardine. (b)ModernversionoftheAnglepoiselamp,theType75.Figure1:TheAnglepoisedesklampisadesignclassicandamechanicalengineeringmarvel.2 1c)Showthatthetotalenergystoredinthesystemisindependentoftheangle.RememberthatthepotentialenergyofamassisUp=mghwherehistheverticaldisplacement,andthatthespringenergystoredinthesespringsisUs=1 2kL2.Hint:Usethecosineruletoexpressthelengthofthespringintermsofa,rand.Also,usethehorizontalpositionofthebaras`zero'con gurationforthepotentialenergyofthemass.1d)Wenowchangetoaslightlymorecomplexbalancer,whichisstartingtoresembletheclassicAnglepoiselamp.Itconsistsofaparallelogram xedtotheworld,andsupportedbyazero-free-lengthspringattachedtothetoparmoftheparallelogram.Itsupportsapayloadmatadistancedfromtheendoftheparallelogram.Drawafreebodydiagramforeachofthecomponents,andshowthatdistancedisirrelevantforthecorrectworkingofthebalancer.NB:youdonotneedto ndexactexpressionsfortheforcestoanswerthisquestion,butacorrectforceanalysisinthefreebodydiagramsisessential! Figure4:TheparallelogrambalanceristhebasecomponentoftheclassicAnglepoisedesign.4 CreatingtheAnglepoiseLampYoucannowquiteeasilyunderstandhowwecancreateanAnglepoiselamp:wesimplyconnectanumberofparallelogramsinseries|seeFigure5.Ifbyanychanceyou'rekeentolearnmoreaboutthemodernAnglepoiselamp,anin-depthmechanicalanalysisisgivenbyFrenchandWidden(2000). Figure5:SchematicofclassicAnglepoisedesign;itworksbyconnectingtwobalancedparallelograms.TheprincipleofcounterbalancingwithspringscanbeappliedtoavarietyofotherproductsbesidestheAnglepoiselamp.Thebalancingarrangemente ectivelymakesapayloadweightless,sotheonlyforcerequiredtomovethemass,istoaccelerateanddecelerateit.Applicationsincludearmsupportsforpeoplewithamusculardiseasewhocannotlifttheirarmwiththeirownmusclestrength,butalsoroboticarmswheretheactuatorscanbelessstrongastheyneednotliftthedeadweightoftheroboticarm.BeforestartinghisPhD,yoursupervisorworkedforacompanythatisdevelopinganadvancedapplicationofthistechnology,thatcaneasilycounterbalancethingslikeTVsandkitchencabinets:http://www.balancebox.eu5 Question2:PuntingthroughJesusLockThisquestionisbasedonaseriesofrealevents...Onceuponatime,onadarkandavery,verycoldNovemberevening, veClaregraduatestudentsdecidedtomovetheMCRpuntsfromtheirberth,tothewinterstorageattheboathouses.AmajorobstacleinthisepicvoyagewastheweiratJesusgreen.Theyallagreedthattakingapuntdowntheonemetredropoftheweirwasprobablynotagoodidea,sotheydecidedtouseJesuslock.Problemwas,noneofthemhadactuallyeverusedalockbefore...buttheythoughttheyoughttobesmartenoughtodealwithsuchasimplecontraption! Figure6:JesusweirandlockinCambridge.Photofromhttp://www.panoramio.com/photo/10225736Theupstreamv-doorswereclosed,sothe rsttaskwastoclosethedown-streamdoors,openthesluicegatesontheupstreamsideandletthelock llup.Duetoastupidmistakebytheoneofthestudents(nevertrustazoologistwithalock),whohadaccidentallypartiallyopenedthelowersluicegatesaswell,ittookforeverto llupthelock.Weallknowtimeisrelative,butwhenit'sverycoldandyou'vebeenpromisedapintaftermov-ingthepunt,timereallyticksveryslowly!Afterabout30minutesoneofthegraduateshadgottenverycoldandalsoratherboredandwhilststaringdownatthelockslowly llingup,concoctedanexamplepaperquestiontoannoyhissuperviseeswith...6