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如图（a）所示，MN、PQ两条平行的光滑金属轨道与水平面成θ＝30°固定在地面上，M、P之间接电阻箱R，电阻箱的阻值范围为0～4Ω，导轨所在空间存在匀强磁场，磁场方向垂直于轨道平面向上，磁感应强度为...
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有一Π形光滑金属导轨倾斜放置两段平行轨道相距L.轨道所在平面与水平面间夹角为a有一垂直于轨道平面向上
如图所示两条足够长的光滑平行金属导轨水平放置导轨上静止地放置两根质量相同电阻相同的导体棒MN和PQ两
最终两导体棒都做匀速直线运动
最终两导体棒都做匀加速直线运动
导体棒 MN 上的电流一直增大
导体棒 PQ 上的电流先不断增大后保持不变
如图所示水平放置的两条光滑轨道上有可自由移动的金属棒PQMN当PQ在外力作用下运动时MN在磁场力的作
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如图所示水平放置的两条光滑轨道上有可自由移动的金属棒PQMN当PQ在外力的作用下运动时MN在磁场力的
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如图所示在水平面内有两条光滑平行金属轨道MNPQ轨道上静止放着两根质量均为m可自由运动的导体棒ab和
如图所示为某一电路的俯视图空中存在着竖直向下的匀强磁场磁感应强度为B.在同一水平面上固定着平行金属轨
如图所示MNPQ是与水平面成θ角的两条平行光滑且足够长的金属导轨其电阻忽略不计空间存在着垂直于轨道平
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如图所示MNPQ为同一水平面的两平行导轨导轨间有垂直于导轨平面的磁场导体abcd与导轨有良好的接触并
如图所示的电路中匀强磁场的磁感应强度为B.在同一水平面上固定着平行金属轨道MN和PQ两轨道间的距离为
如图所示的电路中匀强磁场的磁感应强度为B.在同一水平面上固定着平行金属轨道MN和PQ两轨道间的距离为
如图两光滑的平行金属轨道与水平面成θ角两轨道间距为L.一金属棒垂直两轨道水平放置金属棒质量为m电阻为
如图MNPQ两条平行的光滑金属轨道与水平面成θ角固定轨距为D.空间存在匀强磁场磁场方向垂直轨道平面向
广东省汕头市2017高三第二次4月模拟如图a所示两条平行导轨固定在同一水平面内相距为L.在导轨之间右
如图所示水平放置的两条光滑轨道上有可自由移动的金属棒PQMNMN的左边有一闭合电路当PQ在外力的作用
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如图MNPQ两条平行的光滑金属轨道与水平面成θ角固定轨距为d空间存在匀强磁场磁场方向垂直轨道平面向上
如图所示abc与a/b/c/是两条互相平行且相距为L.的金属轨道其电阻略去不计aba/b/部分在水平
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已知抛物线Cy2＝2pxp＞0过点P30的任意一条直线与抛物线交于AB两点抛物线外一点Qt0若∠OQA＝∠OQB则t的值为
UpcomingMusicfestivalsandconcertsinBostonin2019 NewBedfordFolkFestival2019 The24thAnnualNewBedfordFolkFestivalwillfeaturethebestincontemporarytraditionalandCelticfolkmusic.CalledoneofthemostexcitingandsmartlyprogrammedfestivalsintheNortheastandNewEngland'smostenjoyablefolkfestivalNewBedfordFolkFestivalisanaffordabledestinationforfamiliesseekingafun﹣filledweekend. ●LocationWaterfrontNewBedfordMA ●Phone617999﹣5231 ●DatesSaturdayJuly62019一SundayJuly72019 ●HoursSaturdayandSundayJuly7and8from1100AM.to700PM. ●In/OutdoorOutdoor ●Cost﹩289perfamilylimit4membersperfamily﹩59perticketformorethan4 BostonCallingMusicFestival2019 BostonCallingMusicFestivalisathree﹣daytwo﹣stagefestivalfeaturingsomeofthebiggestandbestactsinlivemusic!!ThemusicalcelebrationtakesplaceattheHarvardSportsComplexwitheasyaccesstostagesawidevarietyoffoodservicesandmore.Allagesarewelcomeandchildrenunder10arefree ●LocationHarvardSportsComplexAllstonMA ●Phone617536﹣4100 ●DatesFridayJuly192019一SundayJuly212019 ●HoursFriday6PM﹣1.1PMSaturday/Sunday12AM﹣I1PM ●In/OutdoorOutdoor ●Cost﹩98perpersonchildrenunder10free LevitateMusic&ArtsFestival2019 JoinusforadayofmusicartfoodandtheoutdoorsattheMarshfieldFairgrounds!Therewillbelotsofmusicarts&craftsanddeliciousfoodtruckstoenjoy! ●Location140MainStreetMarshfieldMA02050 ●Phone617635﹣4505 ●DatesFridayJuly122019•SundayJuly142019 ●Hours1200AM﹣8OOPM ●In/OutdoorOutdoor ●Cost3DayTickets﹣﹩109advanceGA﹩269advanceVIP.Kidsunder12Free JazzintheParkSummerConcertSeries2019 NempacPresentsJazzintheParkSummerConcertSeries2019everyTuesdayfromJuly23thtoJuly30that600prn﹣730pm.Comeandenjoywithus! ●LocationParcel10BostonMA02113map ●Phone617227﹣2270 ●DatesJuly23thtoJuly30th ●Hours600PM一800PM ●In/OutdoorOutdoor ●Cost150perpersonChildrenunder18free. 1Whichfestivalwouldyouliketogoifyouhavespecialinterestinfolkmusic? A.NewBedfordFolkFestival2019. B.BostonCalling.MusicFestival20119. C.LevitateMusic&ArtsFestival2019. D.JazzintheParkSummerConcertSeries2019. 2WhichnumbershouldyoudialifyouwanttolearnmoreinformationabouttheJazzconcert? A.617635﹣4505 B.617227﹣2270 C.617999﹣5231 D.617536﹣4100 3Whatdothefoureventshaveincommon? A.Theyareforfamilies. B.Theylastforthreedays. C.Theytakeplaceoutdoors. D.Theydon'tchargechildren.
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下列不等式中正确的是 ①sinx＜xx∈0+∞②ex≥x+1x∈R③lnx＜xx∈0+∞．
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如图四棱锥S-ABCD的底面ABCD是直角梯形AB∥CDAB⊥BCAB＝2BC＝2CD△SAD是正三角形． 1试在棱AB上找一点M使得BC∥平面SDM 2若平面SAD⊥ABCD在1的条件下试求二面角S-MD-A的正弦值．
＝
若复数是纯虚数则实数a＝．
小明同学在做一项市场调查时的如下样本数据 他由此样本得到回归直线的方程为＝-2.1x+15.5则下列说法正确的是
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Adoverestedonatelephonewire.Readyfortakeoffitraisesitswingsspringsintotheairandflapsaway.Thisseriesofactionsissocommonthatyouprobablydonotpayitmuchattention.ButUniversityofManchesterbioinechanicalengineerBenParslewdoes.Heistryingtodesignrobotsthatcanjumplikebirds. Mostconventionalrobotsrollaroundonwheelslimitingmobility.ThereisaneedformoreagilerobotsthatcanjumpoverobstaclesinmessyenvironmentsParslewsays.TodesignsuchamachineheturnedtonatureBirdsarereallygoodjumpershenotes. Thetroubleiswhenbirdsstarttotakeofftheyleansofarforwardthattheyshouldtipoverandfallontotheirbeaks喙.Yetthatdoesnothappen.Parslewandhisteamusedcomputermodelingtodiscoverhowbirdsavoidthisfate.Theydiscoveredthatbirdstwisttheirbodiesslightlytowardsthebackwhileacceleratingintoajump.Theyalsohaveflexiblelegsandtoejointswhichpreventthemfromtakingoffbrieflyandimmediatelycrashingintotheground.TheresultwerepublishedlastOctoberinRoyalSocietyOpenScience. Parslewthinksengineerscanusethisinformationtodesignrobotsthatcannotonlyjumpwellbutalsolaunchintoflightmore.efficiently.UniversityofSouthernCaliforniabiomechanistMichaelHabibwhowasnotinvolvedinthestudysaysspringsandlevers杠杆enablemorerapidacceleration﹣thanwheelsdo.Andmanyanimalsaremastersofspringsandlevers. IfyoucanunderstandhowthatworksHabibaddsyoucanbuildarobotthat'sgoodatrunningaroundandgoodatflyinganditwillalsobegoodattakingoffsuddenlyinallkindsofconditionsandlandingonadime.Parslewisnowdesigningsucharobotasanalternativetowheeledroversforexploringotherplanets. 1WhatisrightaboutthedovementionedinParagraph1? A.Ittakesoffverybeautifully. B.Itcatcheseveryone'sattention. C.ItgivesBenParslewinspiration. D.ItraisesBenParslew'scuriosity. 2Whatcanwe﹣inferaboutthetraditionalrobots? A.Theycan'tjumpoverbarriers. B.Theycanonlymoveinonedirection. C.Theycan'tdetectbarriersbeforethem. D.Theycan'tadapttocomplexenvironments. 3Howdoesabirdavoidfallingwhentakingoff? A.Bygettingridofgravity. B.Byflappingitswingshard. C.Byspinningitsbodybackward. D.Byjumpingintotheairquickly. 4Whatisthemainideaofthetext? A.Birdsprovideinspiration.forhumans. B.Newrobotsthatcanjumphavebeencreated. C.Thedevelopmentofrobotsbenefitsspaceexp D.Studyingbirds'jumpinghelpsscientistbuildbetterrobots.
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若fx＝2x3+2f'1x-5则f1＝
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速度大小是
加速度大小是
加速度大小是0
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