ExperimentP17:ConservationofLinearMomentum線性動量守恒II(Photogate)（光門Concept:Newton’sLaws概念：定Time:45SWInterface:500&Macintosh_file:P17Cons.ofMomentum2Windows_file:P17_CON2.SWSEQUIPMENTScienceWorkshop_fivepatternpicketfence(photogatemountingbracket(two)光門安裝托架balance(formeasuringmass)天平（用于測量質(zhì)量track,2.2metercollisioncartwithmass(two)帶物塊的碰撞小車PURPOSEThepurposeofthislaboratoryactivityistoinvestigatethemomentumoftwocartsbeforeandafteranelasticcollision.本實驗的目的是研究兩個小車發(fā)生彈性碰撞之前和之后的動量THEORYWhenobjectscollide,whether otives,shopcarts,oryourfootandthesidewalk,theresultscanbecomplicated.Yeteveninthemostchaoticofcollisions,aslongastherearenoexternalforcesactingonthecollidingobjects,oneprinciplealwaysholdsandprovidesanexcellenttoolforunderstandingthedynamicsofthecollision.Thatprincipleiscalledtheconservationofmomentum.Foratwo-objectcollision,momentumconservationiseasilystatedmathematicallybytheequation:當(dāng)物體碰撞時，是機車、運貨小車還是你的腳與人行道發(fā)生 mvmvmvmvIfexternalforcessuchasfrictionareignored,thesumofthemomentaoftwocartspriortoacollisionisthesameasthesumofthemomentaofthecartsafterthecollision.如果忽略外力PROCEDUREForthisactivity,photogateswillmeasurethemotionoftwocartsbeforeandafteranelasticcollision.TheScienceWorkshopprogramcalculatesspeedforbothcarts.在這個實驗中，運動PARTIComputerSetup計算機設(shè)ScienceWorkshop打開如下命名的ScienceWorkshopConnecttheScienceWorkshopinterfacetothecomputer,turnontheinterface,andturnonthecomputer.Connectonephotogate’sstereophoneplugintoDigitalChannel1ontheinterface.ThephotogateconnectedtoDigitalChannel1willbe“Gate1”.Connectthesecondphotogate’ssterepphoneplugintoDigitalChannel2ontheinterface.ThephotogateconnectedtoDigitalChannel2willbe“Gate2”.OpentheScienceWorkshopfiletitledasMacintosh:P17Cons.ofMomentum1Windows:P17_CON2.SWS willopenwithaTabledisplayofVelocity(m/sec)fortwoobjects.文件TheExperimentSetupwindowhasbeenresized.IfyouwanttoexpandtheExperimentSetupwindowtoitsoriginalsize,clickonthe“Zoom”boxintheupperrighthandcornerofthewindow(Note:Tobringadisplaytothetop,clickonitswindoworselectthenameofthedisplayfromthelistatoftheDisplay .)實驗設(shè)置窗口的大小已經(jīng)過PARTII:SensorCalibrationandEquipmentSetup傳感器校準(zhǔn)和儀器Youdonotneedtocalibratethephotogatesforthisactivity.Placethetrackonahorizontalsurface.把軌道放在一個水平面上Levelthetrackbyplacingacollisioncartonthetrack.Ifthecartrollsonewayortheother,usetheadjustablefeetatoneendofthetracktoraiseorlowerthatenduntilthetrackislevelandthecartwillnotrollonewayortheother.把動力學(xué)小車放在軌道上，將軌道調(diào)Putafivepatternpicketfenceinthenotchesateachendoftheaccessorytrayofeachcollisioncart.UsethebalancetofindthemassofeachcartandrecordthevaluesintheDataTable.在每個碰撞小車的附件托盤一端的凹槽中各放一個fivepatternpicketAttacheachphotogatetoaphotogatemountingbracket.MountthephotogatethatisconnectedtoDigitalChannel1(“Gate1”)ontheleftsideofthetrack.Mounttheotherphotogate“Gate2”)ontherightsideofthetrack.將兩個光門分別安裝在兩個光門安裝Placethecartstogetheratthemiddleofthetrack.Positionthephotogatessothat“Gate1”istheleftendofthetwocarts,and“Gate2”istherightendofthetwocarts.Adjustthephotogatessothatthedistancebetween‘gatesisafewcentimetersgreaterthanthetotallengthofbothcollisioncarts.將兩個小車一起放在軌道的。將光門1放在兩Adjusttheheightofeachphotogatesothatasacartmovesthroughthephotogate,the10centimeteropaquebandonthefivepatternpicketfenceblocksthephotogatebeam.調(diào)整每個光門的高度，以一個小車穿過光門時，fivepatternpicketfence上的10厘米不透Movethecartstoeachendofthetrack.10cm

10cm

PARTIIIDataRecording數(shù)據(jù)記Preparetomeasurethemotionofeachcartasitmovestowardtheothercartandthencollideselastically.(Besurethemagneticendsofthecollisioncartswillrepel.)準(zhǔn)備測量ClicktheREC”tobegindatarecording.單擊“RECGentlypushthecartstowardeachotheratthesametimesothattheywillcollideinthespacebetweenthetwophotogates.同時把兩小車向著彼此的方向輕輕推動，使它們在Letthedatarecordingcontinueuntilthecartshavecollidedandreturnedtosofthetrack.繼續(xù)進行數(shù)據(jù)記錄，直到兩小車發(fā)生了碰撞且都返回到軌道末端為止。ClicktheSTOPbuttontoenddatarecording.“Run#1”willappearintheDatalistintheExperimentSetupwindowRun#1將出現(xiàn)在實Repeatthedatarecordingprocedureatotaloffivetimes.將數(shù)據(jù)記錄步驟一共重復(fù)5“Run#5”willbethelasttoappearintheDatalistintheExperimentSetupwindowRunYZINGTHEDATA分析數(shù)TheScienceWorkshopprogramcalculatesthespeedofeachcartbeforeandafteritmovesthroughthephotogateoniteofthetrack.Youcanusetheprogramtocalculatethemomentumofeachcartbeforeandaftercollision,andthetotalmomentabeforeandafter.ClicktheCalculator”buttonintheExperimentSetupwindowtoopentheExperimentCalculator.在實驗設(shè)置窗口中，單擊計算窗口按鈕來打開實驗計算器。CreateacalculationforthemomentumofCart1.Intheformulaarea,typeinthemass(kg)ofCart1(0.5107intheexample),andthenclickthe“multiplication”buttonintheClickthe button.Select“Digital1,Velocity(v)”fromthe 單擊“輸入”菜單按鈕。從輸入菜單中選擇“數(shù)字1，速度(v)”TheformulaistheproductofthemassyouenteredandthemeasuredspeedofCart1.Type“MomentumCart1”intheCalculationNamearea.Type“pCart1”intheShortNamearea.Type“kgm/sintheUnitsarea.Clickthe“equals”buttoninthekeypadoftheCalculator,orpressenteror<return>onthekeyboardtorecordyourcalculation.在“計“單位”區(qū)域中鍵入“kgm/s”。單擊計算器的鍵盤中的“=“按鈕或按下鍵盤上的TocreateacalculationforthemomentumofCart2,clickthe“New”button Repeattheformulacreationprocesswiththefollowingdifferences.創(chuàng)建一個小車2的動量的計算式，Asastep,typeinthemassofCart2andthenclickthe“multiplication”button.第一步，鍵入小車2的質(zhì)量，然后單擊“乘”按鈕。Asasecondstep,clicktheINPUT button,butselect“Digital2,Velocity(v)”fromtheINPUT Tocompletethecalculation,type“MomentumCart2”intheCalculationNameType“pCart2”intheShortNamearea.Type“kgm/s”intheUnitsarea.Clicktheequals”buttoninthekeypadoftheCalculator,orpress<enter>or<return>onthekeyboardto“縮寫名稱”區(qū)域中鍵入“pCart2”。在“單位”區(qū)域中鍵入“kgm/s”TocreatethecalculationfortheTOTALmomentumofbothcartsbeforeandaftercollision,TypeinthemassofCart1andthenclickthe“multiplication”button.ClicktheINPUTbuttonandselect“Digital1,Velocity(v)”.Thenclickthe“addition”button.TypeinthemassofCart2andthenclickthe“multiplication”button.Clickthebuttonandelet“Diital2,Vlociy(v)”.1單擊“輸入”菜單按鈕并選擇數(shù)字，速度v”2的質(zhì)量，然后單擊“乘”按鈕。單擊“輸入”菜單按鈕并選擇數(shù)字，速度v”。Theformulashouldbeliketheexample,butwithyourenteredvaluesforthemassesoftheType“Totalmomentum”intheCalculationNamearea.Type“pTotal”intheShortNamearea.Type“kgm/sintheUnitsarea.Clickthe“equals”buttoninthekeypadoftheCalculator,orpressenteror<return>onthekeyboardtorecordyourcalculation.在“計yzeData分析數(shù)AddcolumnstotheTabledisplayforthemomentumofCart1,themomentumofCart2,andthetotalmomentum.Clickthe“AddPlot” buttonintheleftsideoftheTabledisplay.Select“Calculation,MomentumCart1”fromtheAddPlot 加幾列，分別顯示小車1的動量、小車2的動量和總動量。單擊表左邊的“AddPlot”菜單按鈕，從“AddPlot”菜單按鈕中選擇“Calculation,MomentumCart1”。Repeattheprocesstoaddtheothercolumns.ClicktheAddPlot button.Select“Calculations,MomentumCart2”fromthe .ClicktheAddPlot buttonagain.菜單按鈕，從菜單中選擇“Calculation,MomentumCart2”；再次單擊“AddPlot”菜單按鈕，從菜單中選擇“Calculation,TotalMomentum”。TheTablewillshowthemostrecentrunofdata.ChangetheTabletoshowRun#1.Click“Experiment”inthe bar.Select“Run#1”fromthebottomoftheExperiment .將表改為顯示Run1的數(shù)據(jù)。單擊菜單欄中的“實驗”。從實驗菜單的底端選擇“Run#1”。TheTablewillshowRun#1data.表將顯示Run1RecordthetotalmomentumbeforethecollisionandthetotalmomentumafterthecollisionintheDataTable.將碰撞前和碰撞后的總動量值記錄在數(shù)據(jù)表中。??Remember,valueinthecolumnof“pTotal”isthetotalmomentumcollision.Thesecondvalueisthetotalmomentumaftercollisio