2018PhysicsBowl物理碗真题及答案解析

Divisions1&21Divisions1&2PHYSICSBOWL2018March28–April13,201840QUESTIONS–45MINUTESThesponsorsofthe2018PhysicsBowl,includingtheAmericanAssociationofPhysicsTeachers,areprovidingsomeoftheprizestorecognizeoutstandinghighschoolphysicsstudentsandtheirteachersthroughtheirperformanceonthisyear’scontest.Schoolscompeteinoneoftwodivisions,eachwithnineteenregions.oDivision1isforstudentstakingphysicsforthefirsttime(evenifthatfirstcourseisAPPhysics).oDivision2isforstudentstakingasecond(ormore)courseinphysicsoranyonewantingachallenge.Aschool'steamscoreineachdivisionisthesumofthefivehigheststudentscoresinthatdivision.Aschoolmaycompeteineitherorbothdivisions.INSTRUCTIONSAnswersheet:Writeandbubble-inthefollowingREQUIREDinformationonyouranswersheet:YourNameYourTeacher’sAAPTTeachercode(giventoyoubyyourteacher–onlyonecodeperschool!)YourRegion(giventoyoubyyourteacher)YourDivision(1forfirst-yearphysicsstudents,2forstudentsina2ndphysicscourseorwantingachallenge)Ifthisinformationisnotproperlybubbled,youwillbedisqualifiedasyourofficialscorewillbeazero.YourSchool’sCEEBcode(giventoyoubyyourteacher),thoughnotrequired,IShelpfulintheeventofadisqualificationforidentifyingyourschool.Youranswersheetwillbemachinegraded.Besuretousea#2pencil,fillthebubblescompletely,andmakenostraymarksontheanswersheet.Questions:Thetestiscomposedof50questions;however,studentsansweronly40questions.Answersshouldbemarkedontheanswersheetnexttothenumbercorrespondingtothequestionnumberonthetest.Division1studentswillansweronlyquestions1–40.Numbers41–100ontheanswersheetshouldremainblankforallDivision1students.Division2studentswillansweronlyquestions11–50.Numbers1–10and51–100ontheanswersheetshouldremainblankforallDivision2students.Calculator:Ahand-heldcalculatormaybeused.Anymemorymustbeclearedofdataandprograms.Calculatorsmaynotbeshared.Formulasandconstants:Onlytheformulasandconstantsprovidedwiththecontestmaybeused.Timelimit:45minutes.Score:Yourscoreisequaltothenumberofcorrectanswers(nodeductionforincorrectanswers).Iftherearetiescores,theentrieswillbecomparedfromtheendofthetestforwarduntilthetieisresolved.Thus,theanswerstothelastfewquestionsmaybeimportantindeterminingthewinnerandyoushouldconsiderthemcarefully.GoodLuck!Copyright©2018,AAPTDivision1only2Division1onlyATTENTION:AllDivision1students–STARTHERE.AllDivision2students–Beginonquestion#11.***Treat. forALLquestions#1–#50.1.AquickGooglesearchrevealsthatyourphoneoperatesatafrequencyof850x106Hz.Whichofthefollowingchoicesbestrepresentsthisfrequencyusingmetricprefixes?(A)850Hz(B)850mHz(C)850kHz(D)850MHz(E)850GHz2.Astandardmetalelectroscopeispositivelycharged.Apersonthatisgrounded(neutralcharge)thentouchesthetopportionoftheelectroscopewiththeirfinger.Whichoneofthefollowingchoicesmostcorrectlyexplainswhathappenswhenthefingertouchestheelectroscope?(A)Theleavesoftheelectroscopecomebacktogetherbecauseexcessprotonsconducttothefingerfromtheelectroscope.(B)Theleavesoftheelectroscopecomebacktogetherbecauseelectronsconducttotheelectroscopefromthefinger.(C)Theleavesremainwheretheyareasnothingoccurs.(D)Theleavesoftheelectroscopemoveapartaselectronsconductfromtheelectroscopetothefinger.(E)Theleavesoftheelectroscopemoveapartasprotonsconductfromthefingertotheelectroscope.3.WhichofthefollowingisNOTavectorquantity?(A)Acceleration(B)Averagevelocity(C)Linearmomentum(D)Potentialenergy(E)Force4.Aballisthrownverticallydownwardwithaninitialspeedof12.0m/sfromaheightof10.0mabovetheground.Ignoringairresistance,whatisthespeedoftheballwhenitreachestheground?(A)18.5m/s(B)14.6m/s(C)14.0m/s(D)12.8m/s(E)12.0m/s5.AparticletravelsataconstantspeedaroundacircularpathofradiusR.Iftheparticlemakesonecompletetriparoundtheentirecircle,whatisthemagnitudeofthedisplacementforthistrip?(A)R(B)2R(C)2R(D)4R(E)06.WhattemperatureontheKelvinscaleisequivalentto37oCelsius?(A)310K(B)283K(C)256K(D)37K(E)19K7.Whatisthepercentuncertaintyinthemeasurement2.54±0.16cm?(A)2.9%(B)6.3%(C)8.7%(D)12.6%(E)14%8.AnOlympicbobsledneedstonegotiatea100mradiusturnat35m/swithoutskidding.Whatminimumbankingangleoftheturnisneededforthistohappen?(Ignorefriction.)(A)21o(B)31o(C)41o(D)51o(E)61o9.ThemeandiameteroftheEarthis12.76x103km.WhatisthesurfaceareaoftheEarthinm2?(A)4.01x107(B)5.12x1014(C)1.09x1021(D)1.68x109(E)2.05x101510.A2.0mlongorganpipewhichisopenatbothendsresonatesatitsfundamentalfrequency.Neglectinganyendeffects,whatwavelengthisformedbythispipeinthismodeofvibration?(A)1meter(B)2meters(C)4meters(D)6meters(E)8metersDivisions1&23Divisions1&2AllDivision2studentsSTARTHERE.Numbers1–10onyouranswersheetshouldbeblank.Yourfirstanswershouldbefor#11.***Treat. forALLquestions#1–#50.11.Inaclassroomdemonstration,ateacherdiscussingtheairintheroomasanidealgasslidesasolidbarrierofnegligiblethicknessintoplace,cuttingtheroomintotwoequal-sizedvolumes.Whatistheairpressurefortheportionoftheroominwhichtheteacherisstanding,assumingtheoriginalpressureinthewholeroomwas?Treattheroomasasealedcontainer.(A) (B)(C)(D)2(E)4 12.Whatistheequivalentresistanceinthecircuitthatisshownatright?(A)55(B)80(C)50(D)45(E)7