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一个扇形的面积是12πcm2，圆心角是60°，则此扇形的半径是 cm．
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已知扇形的圆心角为150°它所对应的弧长20πcm则此扇形的半径是_________cm面积是___
已知扇形的圆心角为240º面积为πcm2.1求扇形的弧长2若把此扇形卷成一个圆锥则这个圆锥的轴截面面
一个扇形的面积是12πcm2圆心角是60°则此扇形的半径是cm．
一个扇形的圆心角为120°它所对的弧长为6πcm则此扇形的半径为cm.
一个扇形的圆心角为120°面积为12πcm2则此扇形的半径为cm.
一个扇形的圆心角为30°半径为12cm则这个扇形的面积为.
一个扇形的弧长为10πcm面积为120πcm2则该扇形的圆心角是
一个扇形的圆心角为120°面积为12πcm2则此扇形的半径为cm.
一个扇形的面积是12πcm2圆心角是60°则此扇形的半径是cm．
一个扇形的圆心角为60°它所对的弧长为2πcm则这个扇形的半径为.
扇形AOB的周长为8cm.1若这个扇形的面积为3cm2求圆心角的大小2求这个扇形的面积取得最大值时圆
一个扇形的弧长为20πcm面积为240πcm2则这个扇形的圆心角是
120°
150°
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一个扇形的圆心角为60°它所对的弧长为2πcm则这个扇形的半径为cm.
一个扇形的弧长是20πcm面积是240πcm2则这个扇形的圆心角是度.
一个扇形的面积是314cm2它所在的圆的面积是1256cm2则此扇形的圆心角是
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60°
240°
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一个扇形的面积是314平方厘米它所在的圆的面积是1256平方厘米则此扇形的圆心角是
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60°
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若扇形OAB的面积是1cm2它的周长是4cm则该扇形圆心角的弧度数是____.
一个扇形的弧长是10πcm面积是60πcm2则此扇形的圆心角的度数是
300°
150°
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一个扇形的面积是314cm2它所在的圆的面积是1256cm2则此扇形的圆心角是
180°
60°
240°
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Postingaphotoofthefoodyou'reabouttoeatonWeChathasbecomeadailyritual惯例;仪式formany.Oftenthisfoodinthephotoisn'tasappealingtothoselookingatitbutscientistsarenowclaimingtakingaphotoofyourfoodbeforeyoueatitmakesittastebetter. ResearchersatUniversityofMinnesota'sCarlsonSchoolofManagementclaimtakingaphotoputsyouinthemomentandindoingsoheightensyour41.Thepersontakingthephotowillonsomelevelfeelthemotivationtocontinuethepractice. Researcherswonderedaboutthepowerofritualsafternoticingthefunny42thatpeopleoftenperformbeforeeatinganddrinking.Theyconductedexperimentstoinvestigatewhetherthesekindsofhabitualbehaviourinfluencestaste. Inthefirstexperimentsomeparticipantswereaskedtoeatapieceofchocolatefollowingadetailedsetof43:‘Withoutunwrappingthechocolatebarbreakitinhalf.Unwraphalfofthebarandeatit.Thenunwraptheotherhalfandeatit.'Theotherparticipantswere44instructedtorelaxforashortamountoftimeandtheneatthechocolatebarhowevertheywanted. Theresultsshowedthatthosewhohadperformedtheritualratedthechocolatemore45enjoyeditmoreandwerewillingtopaymoreforthechocolatethantheothergroup. Asecondexperiment46thesefindingsshowingthat47movementsdon'tproduceamoreenjoyableeatingexperience.Thedataalso48thatalongerdelaybetweenritualandconsumptionenhancedtheseeffectsevenwithacommonfoodlikecarrots. Whiletheseritualsmayseeminsignificanttheresearchersnotethattheeffectstheyproducearequiteamazing.Andwhileritualsare49beforemealtimestheycouldplayaroleinother50too.
假定英语课上老师要求同桌之间交换修改作文请你修改你同桌写的以下作文.文中共有10处语言错误每句中最多有两处.每处错误仅涉最一个单词的增加删除或修改.增加:把缺词处加一个漏字符号∧并在其下面写出该加的词.删除:把多余的词用斜线\划掉.修改:在错的词下划一横线并在该词下面写出修改后的词.注意:1.每处错误及其修改均仅限一词;2.只允许修改10处多者从第11处起不计分.Inourlifeweoftenregretwhatwedidandwhichwecouldn'tdo.Actuallyitdoesn'tbenefitusatall.Asformostofuswemissedmanychancetoearnmoremoneytogetahighpositionandtorealizeourdreams.Weoftenregretthatwedon'tseizethoseopportunitiesthusfeelupset.AlthoughwedoknowregrettingthePastisnobenefitbutwestillcan'thelpdoingitToavoidtheproblembelowweneedtopaymoreattentiontowhatyouaredoingnowmakingusbusierandhavingnotimetorecallthepast.Moreoverwe'dbettersetreasonablygoalsonebyone.Onlybydoingsocanwestruggleforourfuturebetter.
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ThereweresomanynightswhenIasayoungboyhadtowatchhelplesslyasmyfatherverballyandphysicallyabusedmymother.Icanstillrecallthesmellofalcoholseethefearinmymother'seyesandfeelthehopelessmiserythatcomeswhenweseepeoplewelovehurtingeachotherinincomprehensibleways. Iwouldnotwishthatexperienceonanyoneespeciallynotachild.IfIsettledowninthosememoriesIcanfeelmyselfwantingtohurtmyfatherbackinthesamewayshehurtsmymotherandinwaysofwhichIwasincapableasasmallboy.Iseemymother'sfaceandIseethisgentlehumanbeingwhomIlovedsoverymuchandwhodidnothingtodeservethepainimposeduponher. WhenIrecallthisstoryIrealizehowdifficulttheprocessofforgivingtrulyis.IntellectuallyIknowmyfathercausedpainbecausehewasinpain.SpirituallyIknowmyfaithtellsmemyfatherdeservestobeforgivenasGodforgiveusall.Butitisstilldifficult.Thesufferingswehavewitnessedorexperiencedliveoninourmemories.Evenyearslatertheycancauseusfreshpaineachtimewerecallthem. AreyouhurtandsufferingIstheinjuryneworisitanoldunhealedwoundKnowthatwhatwasdonetoyouwaswrongunfairandundeserved.Youarerighttobeoutraged.Anditisperfectlynormaltowanttohurtbackwhenyouhavebeenhurt.Buthurtingbackrarelysatisfies.Wethinkitwillbutitdoesn't.IfIslapyouafteryouslapmeitdoesnotlessenthestingIfeelonmyownfacenordoesitweakenmysadnessastothefactyouhavestruckme.Revengegivesatbestonlymomentaryrelieffromouremotionalpain.Theonlywaytoexperiencehealingandpeaceistoforgive.Untilwecanforgiveweremainlockedinourpainandlockedoutofthepossibilityofexperiencinghealingandfreedom;lockedoutofthepossibilityofbeingatpeace. Withoutforgivenessweremaintiedtothepersonwhoharmedus.Weareboundwithchainsofbitternesstrapped.Untilwecanforgivethepersonwhoharmedusthatpersonwillholdthekeystoourhappiness;thatpersonwillbeourjailer监狱看守. Whenweforgivewetakebackcontrolofourownfateandourfeelings.Webecomeourownliberators.Forgivenessinotherwordsisthebestformofself﹣interest.Thisistruebothspirituallyandscientifically.Wedon'tforgivetohelptheotherperson.Wedon'tforgiveforothers.Weforgiveforourselves. 66.Whydidthewritermentionthestoryofhisfather'sabuseofhismom A.Becausehelovedhismomandwantedtofightbacksomeday. B.Becausehisfatherfinallyrealizedhisownmistakeandwasforgiven. C.Becausewitnessinghismom'ssufferingisstillhurtinghimandhasnowaytorelieve. D.Becausehefeltthathewasspirituallyrelievedfromthepainthroughforgiveness. 67.Thewriterwrotethearticleinordertotellpeoplethat. A.wemayneverhealourpainsorsufferingsintheheartunlesswelearntoforgive B.weshouldneverforgetthesufferingsburiedinourhearts C.wemaygettiedtothepersonwhoharmedusallthroughlife D.weshouldn'tworryaboutthepainswecausedsinceforgivingisalwayseasierthanimagined 68.Whatisthe4thparagraphmainlyabout A.Hurtingbackdoesnogoodtorelievingone'sownhurtsbutforgiving. B.Ifsomeoneslapsyouyoujustslapbackwhichwilllessenyourpain. C.Thesufferingswehavewitnessedorexperiencedwillliveoninourmemoriesforever. D.Afterbeinghurtifonewantstoexperiencehealingandfreedomheshouldforgetthehurt. 69.Whichofthefollowingstatementsistheclosestinmeaningtotheunderlinedsentence A.Inordertohelpothersweshouldstopforgivingandfightback. B.Thepurposeofourforgivingisnottohelpotherpeople. C.Ourforgivingisalsousefultohelpingothersthoughtheymayhavehurtus. D.Onlybyforgivingotherscanwehelpthemtobegoodpeople.
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Theorangutan红毛猩猩themostinactiveofthegreatapeshasunusuallystableDNAtoo.Researchershavejustcompletedthesequencing序列oftheentiregenome基因组ofourorange﹣hairedrelativeandtheyhavefoundtotheirsurprisethatitsDNAhaschangedmuchlessdramaticallyovertimethanhasthatofhumansorchimpanzees.TheorangutanisveryuniquesaysDevinLockeastructuralgeneticistheadingtheorangutansequencingproject.Theorangutangenomehadoneotherbigsurprise.LockeandcolleaguessequencedsixSumatranandfiveBorneanorangutanswhichareclassifiedasdifferentspecies.Theapeshavebeenphysicallyseparatedforatleast21000years﹣thelasttimelandbridgesbetweenthetwoislandsexisted﹣andearlierstudiesestimatedthattheybecamedistinctspeciesmorethan1millionyearsago.ButthenewanalysisreportedonlinetodayinNaturerewriteshistory:itappearstheypartedwaysjust400000yearsago.MostpreviousstudiesusedsmallsetsofmarkersandalimitedamountofDNAsequencesaysLocke.Thestatisticalpowerissomuchgreaterwhenyouhavethewholegenomeavailable.Theorangutannowjoinschimpanzeesandhumansasthethirdgreatapetohaveitsgenomesequenced.TheorangutangenomeisawonderfulresourcesaysevolutionarygeneticistSvantePääbooftheMaxPlanckInstituteforEvolutionaryAnthropologyinLeipzigGermany.ItwillhelpclarifyhoweachpartofhumanandAfricanapegenomesarerelatedtoeachotherandevolved.Suchinsightsarealreadycomingin.Orangutansoriginatedsome12millionto16millionyearsagogivingtheirgenomesmuchmoretimetoevolvethanthoseofhumansandchimpanzeeswhichsplitintotheirownlineages血统5millionto6millionyearsago.Butacomparisonofthethreegenomesshowsthathumansandchimpanzeesloseorgainnewgenesattwicetherateoforangutans.ThereasonmayhavetodowithstretchesofDNAcalledretrotransposons.Thesekeydriversofevolutionjumparoundthegenomecreatingnewgenesdamagingexistingonesoralteringgeneregulation.ThenewdatarevealthatcommonretrotransposonsknownasAluelementshavemovedaroundtheorangutangenomemuchlessthantheyhaveinthehumanandchimpanzeegenomes.Idon'twanttosaythat‘Aluretrotranspositionevents'areshutoffinorangutansbutthey'vebeencoveredupsaysLocke.Theresearchersalsodiscoveredthatovertimethestructureoforangutanchromosomes染色体haschangedlittlewhichmaybelinkedtotheAluelementfinding.Otherresearchershavesuggestedthatthestrongandhealthystructuralvariationinhumansandchimpsmayhavestimulatedincreasedintelligence.ButLockenotesthatorangutansarealsohighlyintelligent.Iforangutanshavehadverylittlestructuralvariationmaybethisdecouplesstructuralvariationfromintelligencehesays.AseparatebutrelatedstudypublishedtodayinGenomeResearchreportsyetanotherunexpectedfindingfromacomparisonofthethreegreatapegenomes.AteamledbyMikkelH.SchierupandThomasMailundofAarhusUniversityinDenmarkbothco﹣authorsoftheNaturereportdiscoveredthatsomeregionsofthehumangenomemorecloselyresembletheorangutanthanthechimpanzee.ThisreflectsthefactthatatthetimehumanssplitofffromacommonancestorwithchimpsbothspecieshadthesameancestralorangutanDNA.Buthumansandchimpanzeeshaveevolvedseparatelyformillionsofyears.IntheprocesschimpsformysteriousreasonslostsomeorangutanDNAthathumanskeptpossessionof.Moresurprisesaresuretocomeasresearcherscomparethegenomesofevenmoreapes.Projectstosequencetheothertwogreatapesgorillasandbonobosareunderway.74.OrangutansfromtwoislandsSumatranandBorneanbecamedifferentspeciessince.A.atleast21000yearsagoB.over1millionyearsagoC.some12millionto16millionyearsagoD.400000yearsago75.WhichofthefollowingstatementsisTRUEaccordingtothispassageA.ComparedwiththeDNAoforangutanchimpanzee'sislesschangedovertime.B.Onlythreeapes'genomeshavebeensequenceduptonow.C.Humans'ancestorssteppedontheirwayofevolution12to16millionsyearsago.D.Chimpanzeesgainnewgenesfasterthanorangutansdoinevolution.76.Thereasonoforangutan'slittlechangeinDNAisthat.A.thisspeciesisnotasactiveinintelligenceashumansorchimpanzees.B.thenewlyidentifiedAluelementsisbelievedtohaveplayedaspecialroleC.AluretrotranspositionsinorangutanareshutoffduringthecourseofevolutionD.orangutan'slowintelligencefailstostimulatethechangeofitsDNA77.Someregionofhumangenomeismoresimilartothatoforangutanthanchimp'sbecause.A.humanandorangutansharethesameancestorbutchimpdoesn'tB.humansandchimpanzeeshaveevolvedseparatelyformillionsofyearsC.chimpsfailedtohangontoorangutanDNAforsomeunknownreasonbuthumandidn'tD.chimpsdidn'tactasactivelyashumansresultingintheirlosingsomecriticalorangutanDNA.
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Pickingauniversityisatenseperiodofaskingyourselfwhichinstitutionismostrelevant.That'swhyuniversityrankingsplaysuchavitalroleinstudentssearchingfortheirnextacademicdirection.Rankingsarealsoaninescapablepartofthereputationandbrandimageofuniversities.Nouniversitywebsiteiscompletewithouttheclaimtobeinthetop100forsomethingorotherreportedtheBBC.Thereasonissimple:Rankingshelpthemtoattractstudentsstaffandresearchinvestment. Currentlytherearenumbersofuniversityrankingsandeachhasitsownlistofcriteria.Butthemaincategoriesarethesame:academicreputationgraduates'performanceandfacultyresources. Howeverexpertspointouttherankingprocessisn'tentirelyreliable.MarkKantrowitzaUSfinancialaidresearchersaiduniversityrankingsweremostlyjustforshow.HewroteinTheNewYorkTimes.Itmaygiveyourparentsbetterbraggingrightsbutthat'saboutit. Moreoverit'snotdifficulttoseethelimitationsofuniversityrankings.Manyrankingsfocusonthenumberoftimesresearchworkiscited引用byotherresearchers.IthelpsBritishandUSuniversitiestodominateglobalrankingsbecauseEnglishisthefavoredlanguageofacademiaJohnO'LearyamemberoftheQSacademicadvisoryboardtoldTheGunrdian.AlsorankingssuchasQSmainlyfocusonthequalitiesoftheuniversityratherthanitsstudents.AnyuniversityrankingislikelytohelpstudentsmakebetterdecisionsaboutwheretostudybuttheneedtobalancethemwithothermorehumanfactorsisalsoimportantsaidPhilMossaneducationandadmissionsconsultant.Advicefromgraduatesorcurrentstudentscanbeasvaluableinprovidingagenuineinsightintotheexperienceorqualityofaparticulardegreeprogram.Itcanalsoaddanelementthatrankingscanneverconvey﹣﹣theactualemotionofauniversityexperience. 32.WhydouniversitiesconsiderrankingsimportantA A.Rankingsmakethemmoreappealing. B.Rankingsarestudents'onlyreference. C.Rankingscanincreasetheiracademiclevel. D.Rankingshelpthemcompletetheirwebsites. 33.WhatdoestheunderlinedItinparagraph4refertoC A.Acadenucresearchwork. B.Thenumberofresearches. C.Thewayofrankinguniversities. D.Thelimitationofuniversityranking. 34.AccordingtoJohnO'LearywhathelpsBritishandUSuniversitiesrankwellA A.ThewideuseofEnglishinacademia. B.Theiroutstandingqualities. C.Theirgraduates'excellentperformance. D.Theacademia'sfavortothem. 35.BesidesrankingwhatdoesPhilMosssuggestyoushouldrefertoifyou'repickingauniversityD A.Investmentineducation. B.Guidancefromprofessors. C.Informationonwebsites. D.Suggestionsfromstudents.
小明参加科技节“掷飞机”比赛该项目的规则是纸飞机掷出后在空中滞留的时间越长成绩越好．查阅资料得知纸飞机在空中滞留的时间与其形状质量出手速度和出手角度有关．小明认为还可能与纸飞机表面的粗糙程度有关．为了验证自己的猜想小明准备了以下器材进行实验研究 发射器如图秒表剪刀面积质量大小和表面粗糙程度不同的两种纸AB各若干张同种纸正反面粗糙程度相同． 1发射器的弹簧压缩得越短释放后纸飞机获得的速度越大其原因是． 2写出本实验的主要步骤．
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窗玻璃上趴着一只壁虎如图水平向右推窗当壁虎随窗玻璃一起向右匀速移动的过程中壁虎受到摩擦力的方向是
这部滑稽的电影的确分散了我注意力让我暂时忘记了这些难题.which.
NotbeingsurewhereIwanttostartthisIwillsaythatIlostmymombackinAprilofthisyear.Shewasninety﹣two.41Iwasnotexpectingherto42andIdon'tthinkshewasexpectingiteither.Iwasveryclosetomymombeinganonlychild.Wedidhave43onthesurfacebutwestillhadacloserelationship44those. Beingnewlymarriedlessthanayearandhavingmovedacoupleoftimes45Ihavehadmorechangesrecentlyinmylifethanatanyotherpointofmyfifty﹣fouryears.StabilityisoneofthegiftsthatMom46meandithadsomany47thatIwasn'tawareofuntilnow.MyhusbandandIhavemadesome48toMom'shomeandwillbemovingattheendofnextweek.Itisnowourhomebutitstillhasmy49heartinit.It'swhereIgrewupandtherearemany50thatwilllivetherewithus.AtthesametimeIamlookingforwardto51someveryhappyandmemorableoneswithmyhusband. Mom52suchabigpartinmylife.Ourliveswere53wovenbecauseshegavemehervalueswhichhavebecomestrongly54inthewomanIamtoday.Idon'thaveanychildrenwhomIcould55theseonto.HoweverMother'svaluesaffectmeeverydaywiththe56IhavewithotherswhetherIknowthemornot.IhopeMomwouldbe57ofwhoIamwhatI'vebecomebecauseofherandof58Iamgoingtolivewithmy59.ShegavemeeverythingIneededtoknowinlife:respectothersandgivehelptootherswho60itmost.IloveyouMomandIwillneverforgetyou. 41.A.However B.Otherwise C.Moreover D.Though 42.A.passout B.passaway C.passby D.passdown 43.A.promises B.agreements C.differences D.similarities 44.A.intermsof B.incaseof C.inneedof D.inspiteof 45.A.once B.since C.though D.either 46.A.saved B.brought C.gave D.taught 47.A.ideas B.thoughts C.meanings D.benefits 48.A.studies B.decisions C.changes D.remarks 49.A.son's B.father's C.mom's D.husband's 50.Amemories B.chances C.choices D.dreams 51.A.receiving B.promising C.making D.supplying 52.A.affected B.played C.controlled D.managed 53.A.brightly B.lightly C.roughly D.tightly 54.A.intended B.designed C.rooted D.admitted 55.A.hold B.pass C.drive D.reply 56A.contact B.interest C.trouble D.effect 57.A.free B.proud C.full D.certain 58.A.what B.where C.why D.when 59.A.life B.children C.husband D.time 60.A.hunt B.need C.treat D.consider
小明制作了一个如图所示的简易气压计．将橡皮膜平铺在敞口容器上并用胶带绑紧．检查气密性后将吸管的A端粘在橡皮膜中心B端靠近卡纸的M处．外界气压的变化会引起橡皮膜凹凸程度的变化从而使吸管绕O点转动指示气压大小变化．外界气温的变化对容器内气压的影响极小 1检查气密性时将绑有橡皮膜的容器浸没在水中轻压橡皮膜如果观察到则气密性不好． 2小明将该气压计从甲地带到乙地发现吸管B端的指向从M处变为N处．则甲乙两地气压较大的是．
温州地区常受台风侵袭为测量风速小明设计了一台简易风速仪其工作原理如图甲所示．装有挡风板和滑片P的轻质滑块与轻质弹簧套在滑杆MN上弹簧左端固定右端与滑块相连．挡风板的挡风面积为0.2米2均匀电阻丝AB长为20厘米阻值为10欧电源电压U0恒为6伏保护电阻R0为14欧电压表量程0～3伏．弹簧弹力F与弹簧长度改变量x的关系如图乙所示．无风时滑片P在A处有风时滑块移动稳定后读出电压表示数计算并查阅下表数据可知风速及风级． 表中风压p是指与风向垂直的受风面上单位面积增加的压力即单位面积受到的风力．测量时保证风垂直吹在挡风板上不计一切摩擦阻力． 1在滑片P左移的过程中电路的总电阻．选填“变大”“不变”或“变小” 2当电压表示数U为2伏时风速仪所测的风为几级写出计算过程 3小明想在风速仪的电压表上直接标出风速查阅资料后获知该挡风板所受的风力与风速的平方成正比．经计算他画出了风速v与电压表示数U的关系曲线如图丙所示．后因保护电阻R0损坏他将其换成了阻值为5欧的电阻请你在图丙坐标系中大致画出更换电阻后的风速v与电压表示数U的关系曲线并在曲线上标出所能测量的最大风速的对应点Q．
众所周知大量砍树对自然平衡有灾难性的影响.As.
小敏对“物体在水中浸没前受到的浮力是否与浸入深度有关”进行了研究． 1将一长方体金属块横放部分体积浸入水中时在液面所对的烧杯壁作一标记线读出弹簧测力计的示数F甲如图甲为牛再把金属块竖放浸入同一杯水中当时读出弹簧测力计示数F乙如图乙．比较发现F乙＝F甲小敏得出浸没前物体受到的浮力与浸入深度无关． 2图中两种状态时金属块底部受到水的压强p甲p乙选填“大于”“等于”或“小于”．
AroundfouryearsagoIreceivedacallfromtheprincipalofourschoolastotheParentsViewtalkthenextmorning.Heaskedmetospeaktothegroup.Afterthecallmywholebodybecamefeverishandpanicky.Thetimefromhiscalltothenextmorningseemedlikeyears.ThewholenightIcouldnotsleepwithmanyominousapprehensionsinmind.OneofthemwastocalltheprincipalwithregretandtellhimthatIcouldnotcome.FinallyIgatheredsomecourage.IthoughtIfImissthisopportunitysurelytheschoolwillneverinvitemeagaintoanyoftheirprograms.Ireachedtheschoolintime.Beforemyturncamemywholebodywastrembling.WhenmyturncameandIstartedspeakingmyheartbeatincreasedandmymouthwentdry.Iwasn'tevenabletoreadthewrittenspeechproperly.IwasnotawareofwhereIwasstandingandwhatIwasreading.ThatwasthedaywhenIrealizedmybiggestweaknessPublicSpeaking.AftermyspeechImetwiththeprincipalandexplainedwhathappenedtome.Hetoldmethatthishappenstoeveryone.Evengreatspeakerfacedthesamethingswhentheystarted.HesuggestedthatIcomeagainnexttime.AroundonemonthlaterIwasinvitedtorefertoatopiconMotivation.ThistimeIwasfeelingcomfortable.MyspeechwasnotonlyappreciatedbytheprincipalaswellastheteachersbecauseIwasabletogetmyideaacrosstothem.Theyencouragedandpraisedmyefforts.AfterdeliveringissuccessfullyIbecamemoreconfident.lsaidtomyselfIfIcanspeakinfrontofsuchalearnedaudienceliketheprincipalwhoeducatesothersIcannowspeakinfrontofotherstoo.IstarteddeliveringlecturesinmyplantonvarioustopicslikeSelfMotivationPersonalityDevelopmentPersonalExcellenceSpokenEnglishandPresentationSkills.Thishasbecomeapassionforme.Ilearnedthateverythingispossibleifwehavethecouragetotakethefirststep.24.WhichofthefollowingisthehesttitleforthepassageAA.PracticeMakesaManaBetterSpeechmakerB.PublicSpeakingMakesaManEmbarrassed.C.PrincipalProvidestheBestChances.D.SpokenEnglishDevelopsinMaltingSpeeches.25.TheauthorhadbadfeelingsbeforethespeechbecauseD.A.hedislikedtheideaofgivingalectureB.hehadgotahighfeverbeforethatC.heregrettedacceptingtheinvitationD.hefearedhecouldn'tperformitproperly26.WhatdoestheunderlinedpartominousapprehensionsinthefirstparagraphmeanBA.Unluckyopportunities.B.Negativeideas.C.Curiousviews.D.Happycomments.27.WhatcanweconcludefromthepassageCA.Nothingistobegotwithoutpainsbutpoverty.B.Knowledgemakeshumbleignorancemakesproud.C.Ajourneyofathousandmilesbeginswithasinglestep.D.Necessityisthemotherofinvention.
如图所示固定的轻弹簧下端用细线竖直悬挂一条形磁体当下方电路闭合通电后发现弹簧长度缩短了请在括号中标出螺线管下端的极性N或S和电源上端的正负极+或﹣．
如图中所示电路中已知定值电阻R1＝20Ω开关闭合后两个完全相同的电流表A1A2指针均指在同一位置如图乙所示则此时通过R1的电流为A在10s内R2产生的热量为J．
我们每天都在产生大量垃圾合理分类和利用垃圾是我们面临的一个重大课题．某垃圾处理厂处理垃圾时提炼出了200kg燃料油若燃料油的热值为4.0×107J/kg则这些燃油完全燃烧放出的热量为J燃料油燃烧时发热燃料油的化学能转化为能．
在测量小灯泡的电功率的实验中实验室提供如下器材电源电压恒为6V电压表和电流表各一个额定电压为2.5V的待测小灯泡L电阻约为10Ω滑动变阻器两个R甲10Ω1AR乙50Ω0.5A开关S导线若干．1该实验的原理是电功率P＝2实验中应选用的滑动变阻器是选填R甲或R乙3选用滑动变阻器后请你根据以上器材设计一个测量小灯泡电功率的实验电路图并画在图甲的虚线框内4某小组在实验中记录了3组小灯泡的电流随电压变化的情况如图乙所示完成实验后小组进一步求得该小灯泡正常发光时的电阻为Ω保留到小数点后一位5另一小组实验时发现电流表已经损坏为了测出该小灯泡的额定功率小组在实验室选了一个10Ω的电阻R0和一个单刀双掷开关设计了如图丙所示的电路并完成了该实验电源电压不变①闭合开关SS1接b调节滑动变阻器R使小灯泡正常发光记录电压表示数U1．②闭合开关S滑动变阻器滑片保持不动S1接a读出此时电压表示数为U2．则小灯泡额定功率P额＝用R0U1U2表示．
雾天能见度低骑车易发生交通事故要减速慢行． 1雾天空气中会形成大量水珠．该过程发生的物态变化是 2小明要为自行车设计一种“雾灯”以提示过往的行人和车辆．要求工作时灯泡能持续交替闪烁忽 略弹性衔铁和电磁铁线圈电阻下列电路中符合设计要求的是．
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