英语课发言稿.docx

英语课发言稿

第一篇：英语课发言稿Goodmorningeveryone,mynameisZhouJianshuo.Today，mytopicisSlingshoteffect,physicsinAstronomy.Slingshoteffect,inChinesewecallit“引力弹弓效应”，isanastronomicaltechnologyusedinthefieldoftheinterstellartravel,inChinesemeans“星际航行”TheoriginofSlingshoteffectdatesbacktotheearly1920s,whenafamoussovietscientistcalled尤里·康德拉图克,firstcameupwiththisidea.Inshort,itworkslikethis.Supposethatyouwanttoarriveatanextremelyremotelocationinspace，here，wecallitlocationA（画上），becauseitissofarfromyouthatyoucannotheadtoitinnormalway，oryouwilldiebeforeyoureachit.Allyouneedisabigplanet，whichislocatedinthelocationB（画上）Thenyouneedtomakeyouraircraftmoveinthespecificorbit,likethis.(画一半)Thisorbitandthespeedmustbeveryaccurateinordertoacceleratetheaircraftbythegravityoftheplanetwiththeleasttimeandfuel.Thentheaircraftwillmovelikethis(画上),reachingthedestinationwithaveryfastspeed.Thatistheslingshoteffect.Thephysicaltheoryoftheslingshoteffectistheconservationofmomentum,inChinesecalled“动量守恒”。Theschematicislikethis.A“stationary”observerseesaplanetmovingleftatspeedUandaspacecraftmovingrightatspeedv.Ifthespacecrafthasthepropertrajectory,itwillpassclosetotheplanet,movingatspeedU+vrelativetotheplanet'ssurface.Whenthespacecraftleavesorbit,itismovingatspeedU+vrelativetotheplanet'ssurfacebutintheoppositedirection.SincetheplanetismovingleftatspeedU,thetotalvelocityofthespacecraftrelativetotheobserverwillbethevelocityofthemovingplanetplusthevelocityofthespacecraftwithrespecttotheplanet.Sothevelocitywillbe2U+vSlingshoteffectisfrequentlyusedinastronomy.Forexample,In1974,TheMariner10probewasthefirstspacecrafttousethegravitationalslingshoteffecttoreachanotherplanet,onitswaytobecomingthefirstspacecrafttoexploreMercury.Noonecanconcealthefactthatslingshoteffectexertsatremendousinfluenceonthecurrentastronomicalresearch.AndthetechnologieswhichusethebasicphysicaltheoryplayanessentialpartinScience.Thatistheendofmypresentation,Thankyouverymuch.第二篇：竞选英语课代表发言稿竞选英语课代表发言稿(15篇)竞选英语课代表发言稿1敬爱的老师、亲爱的同学们：大家好！今天我要竞选的职务是英语课代表。拿破仑说过