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-3的相反数与的倒数之和为
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电路中串联电容的总电容的等于各部分电容倒数之和
相反数
倒数
平方
开平方
-4.5与互为相反数0的相反数是+3的倒数的相反数是的相反数是
下列说法正确的是
有理数的绝对值为正数
只有正数或负数才有相反数
如果两数之和为0，则这两个数的绝对值相等
任何数都有倒数.
－3的倒数是相反数是.
﹣7的绝对值的相反数的倒数为.
已知ab互为相反数cd互为倒数m的相反数是的倒数则的值为_________.
关于相反数的叙述错误的是
两数之和为0，则这两个数为相反数
如果数轴上两数所对应的点到原点的距离相等，则这两个数互为相反数
符号相反的两个数，一定互为相反数
零的相反数为零
下列说法中不正确的是
一个数与它倒数之积是1
一个数与它的相反数之商为-1
两个数的商为-1，这两个数互为相反数
两个数的积为1，这两个数互为倒数.
下面用数学语言叙述代数式-b其中表达不正确的是
比a的倒数小b的数
1除以a的商与b的相反数的差
1除以a的商与b的相反数的和
b与a的倒数的差的相反数
-1.5的相反数为________倒数为________.
下列说法不正确的是
一个数（不为0）与它的倒数之积是1
一个数与它的相反数之和为0
两个数的商为﹣1，这两个数互为相反数
两个数的积为1，这两个数互为相反数
－3的相反数是__________－3的倒数是___________.
已知数a－2与2a－3.1若这两数互为相反数则a的倒数是________相反数是________.2
串联电容的总电容的等于各部分电容器倒数之和
相反数
倒数
平方
开平方
电阻并联后等于各支路电阻的倒数之和
总电阻
总电阻的倒数
总电阻的相反数
电阻
－3的相反数是倒数是
若a与b互为相反数c与d互为倒数则a＋b＋3cd＝_
的相反数为__________倒数为__________
-3的相反数是________倒数是____________.
串联电容的总电容的等于各部分电容倒数之和
相反数
倒数
平方
开平方
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如图中abcde为元素周期表中前四周期的一部分元素下列有关叙述正确的是
燃料电池的基本组成为电极电解质燃料和氧化剂．此种电池的能量利用率可高达80%产物污染也少．下列有关燃料电池说法错误的是
如图所示传送带的右边平滑对接倾角为30°的光滑固定的斜面左边对接固定的挡板传送带ab的长度l＝2.0m它始终以v＝3.0m/s的速度顺时针转动．现将一个可视为质点的小物体由c点静止释放bc距离L＝1.4m小物体与传送带表面的动摩擦因数取g＝10m/s2．求 1小物体运动到传送带的下端a点时的速率 2若小物体与挡板相撞时无机械能损失试通过计算说明小物体能否与挡板发生第二次相撞．
下列各分子中所有原子都满足最外层为8电子结构的是
以下说法正确的是
Thetermtoextendanolive橄榄branchmeanstomakeanofferofpeaceorreconciliation和好.ThistermhasBiblicalshèng jīng 的originscomingfromthesectionoftheOldTestamentthatdealswiththefloodthesignthatthefloodisoverisanolivebranchbroughtbacktotheark方舟byadove.OlivebrancheswerealsosymbolsofpeaceinAncientGreeceandRomeandtheycontinuetobeusedinvariousworksofartthataremeanttosuggestpeace. Somepeoplehavesuggestedthattheolivewasaverydeliberateandwell﹣consideredchoiceasametaphor比喻forpeacebecauseolivetreesfamouslytakeyearstomature.Waristypicallyveryhardonthetreesbecausepeoplecannottakethetimetonurturethemandplantnewones.Thereforetheofferofanolivebranchwouldsuggestthatsomeoneistiredofwarwhetheritisanactualwarorafallingoutbetweenfriends. InAncientGreekandRomantimespeoplewouldofferactualolivebranches.InRomeforexampledefeatedarmiestraditionallycarriedolivebranchestoindicatethattheyweregivinginandtheGreeksusedthemintoweddingsandotherceremonies.Inthemodernerathebranchisusuallymetaphoricalratherthanactualnotleastbecausetheplantscanbeabitdifficulttoobtain. Manypeopleagreethatpeacenegotiationsatalllevelsofsocietyareagoodidea.Betweennationsobviouslyitisimportanttoextendanolivebranchtoensuremutualsafetyandtohelptheworldrunmoresmoothly.Thisactcanalsobeimportantonapersonallevelasresolvingconflictandlearningtogetalongwithothersisviewedasanimportantlifeskillinmanycultures. Atsomepointintheirlivesmanypeoplewillbeadvisedtoextendanolivebranchtosettleadisputeorresolveanissue.Somepeoplebelievethatittakesanimmenseamountofcouragetotakethisactionasitoftencomeswithanadmissionofwrongdoingandregret. 32.AccordingtotheBible. A.anolivebranchsuggestsfloodiscoming B.thearkismadeofolivetreewood C.anolivebranchmeansfloodisover D.adovelovestosettleontheolivebranch 33.TheoliveisconsideredagoodchoiceasametaphorforpeaceforthefollowingreasonsEXCEPT. A.olivetreesfamouslytakeyearstomature B.olivebranchesmakepeopletiredofwar C.waristypicallyveryhardonthetrees D.peoplecannottakethetimetonurturethemwhileatwar 34.Whyareactualolivebranchesseldomusedinmoderntimes? A.Olivetreesarebeingprotectednow. B.Olivetreesareplantedonlyincertaincountries. C.Olivetreescanbefartoseek. D.Thereisnoneedtouserealolivebranches. 35.Itcanbelearnedfromthetextthattoextendanolivebranch. A.isnotimportantonapersonallevel B.isonlyimportantbetweennations C.takesalotofcourage D.isanimportantlifeskillinmanycultures.
Listedherearefourofthethousandsofimpressivemuseumsaroundtheworld. TheGuggenheimMuseumBilbaoinBilbaoSpain Builtin1997theGuggenheimMuseumBilbaoisoneofthenewestintheworld.IthastransformedtheindustrialcityofBilbaointoatraveler'sdesireddestination.Thebeautifularchitectureofthemuseumhasprovidedadramaticbackgroundformoviesandcommercials. TheLouvreinParisFrance ProbablythemostfamousLouvrealsoholdsthemostfamouspaintingintheworldtheMonaLisabyLeonardodaVinci.Crowdscanbefoundanydaysurroundingthesmallbutmysteriouspaintingofthesmilingwoman.ButtheLouvreismuchmorethanahometotheMonaLisa.TheLouvreisvisitedbymorepeopleeachyearthananyothermuseumintheworld. TheBarnesFoundationinPhiladelphiaAmerica Justopenedinitsnewdowntownlocationin2012theBarnesFoundationisuniqueinthatitisacompletelyreproduceddisplayfromoneman'sprivatecollection.Dr.AlbertC.Barnesstartedcollectingartintheearly20thcenturyandcollectedamongothersthelargestnumberoforiginalRenoirpaintingsintheworld. TheUffiziGalleryinFlorenceItaly Walkingonthemarbledfloorsfeelslikesteppingbackintime.Thebuildingitselfisabeautifulpalace﹣likestructurewithfrescoes湿壁画decoratingtheceilingsandwalls.Viewersarebowledover印象深刻bytheworksbyBotticellisuchasTheBirthofVenus.Classicartworksfromnearly1000yearsagodescribereligiouseventsofthetime. 21.Whichofthefollowingisthemostpopular? A.TheLouvre. B.TheGuggenheimMuseumBilbao. C.TheBarnesFoundation. D.TheUffiziGallery. 22.WhatmakestheBarnesFoundationparticular? A.Itsstructure. B.Itscollection. C.Itslocation. D.Itshistory. 23.Whattypeofwritingisthistext? A.Anactivityposter. B.Anexhibitionannouncement. C.Anartshowreview. D.Atravelguide.
Ihadbeenstaringatthewhitewallsofthevideogamestoreforabout2hourssincelunch.Itwasavery41day.Iglancedatthetableinfrontofthestoreandmyheart42.ItwasthedonationtableforthevictimsofTyphoonYolandaandeventhoughIhaddonatedwhatIcouldI43feltsadwheneverIsawthepeopleontheTVsuffering. Iwasbrokenoutofmy44whenthedoorsgotopen.Customers45! Shewasasmallgirlabout10or11.Hermotherwasaccompanyingherwithafewplasticbags.I46hermom.WhenIwassellingcigarettesonthestreetIsawhersellingclothesshe47herselfatthemarket. Thedaughterjusthada48andhermomfinallyhad49moneytobuyaPS3andsomegames. Thegirlhalf﹣joggedhalf﹣skippedtomycounter.She50herbackpackandpulledoutaconsole操纵板.Hermomhandedmethebagfullofgames. CanI51this? Suresweetienoproblem. Iinspectedtheconsoleandthegamesandnothingwasopened.Accordingtoour52Ireturnedthe53tothemom.Shehandedittothegirl.Andthegirlranoffasfastasherlittlefeetcouldtakeher.Iwasabouttoaskwhenthemomseeingmy54explainedShewantstosellherbirthday55soshecandonatetothe56. Shewas57togiveupwhatwassupposedtobehersandgavetothose58.That'srealgenerosityoutthere. 59IwaswatchinghertalkingtothegirlatthedonationstableIwasremindedthateventhoughtherearealotof60peopleintheworldtherearestillthosepeoplejustlikethatlittlegirl. 41.A.good B.cold C.warm D.slow 42.A.beat B.ached C.ran D.sank 43.A.almost B.also C.still D.never 44.A.moods B.dreams C.pains D.thoughts 45.A.firstly B.finally C.quickly D.excitedly 46.A.greeted B.found C.recognized D.told 47.A.wore B.made C.washed D.bought 48.A.date B.job C.birthday D.disease 49.A.enough B.little C.easy D.big 50.A.carried B.opened C.sold D.left 51.A.buy B.change C.return D.donate 52.A.plan B.decision C.discussion D.regulation 53.A.money B.backpack C.games D.receipt 54.A.smile B.expression C.unhappiness D.difficulty 55.A.card B.cake C.surprise D.gift 56.A.victims B.workers C.charities D.typhoons 57.A.grateful B.willing C.unhappy D.afraid 58.A.poor B.unfortunate C.indanger D.inneed 59.A.Since B.Until C.While D.Although 60.A.selfish B.unlucky C.poor D.rich
假定你是李华是你校读书俱乐部的负责人计划在下个月组织英语读书节. 请给你的美国笔友Tony写信介绍本次活动并请他为本次读书节推荐阅读书目. 注意 1.词数100左右 2.可以适当增加细节以使行文连贯 3.信的开头和结尾已给出不计入总词数. DearTony Lookingforwardtoyourearlyreply! Yours LiHua.
SashaObamadaughterofUSPresidentBarackObamahasswappedthecomfortsoftheWhiteHousefor61seafoodrestaurant. The15﹣year﹣old62takeasummerjobservingfoodatthebusinessinMartha'sVineyardMassachusettsrecently.Sashausing63fullnameNatashahasbeenaccompaniedtotherestaurantbyateamofsixsecretserviceagentstheBostonHeraldreports. Thetownhasbeenafavorite64locatefortheObamasontheirsummerbreaks.Photographsshowthepresident'syoungestdaughter65weartherestaurant'suniformofblueT﹣shirtandcapandworkingatatill在收银. Aco﹣workertoldtheHeraldShe'sbeenworkingdownstairsattakeout.Wewerewondering66thereweresixpeoplehelpingthisgirlbutthenwefound67whoitwas. TheWhiteHousehasnotcommentedonthereportbutFirstLadyMichelleObamahasspokenabouttryingtobringhertwodaughtersupas68normalaspossible. AswellasworkingonthetakeawaycounterSashaObama'sother69dutyreportedlyincludewaitingontablesandhelpingtopreparetherestaurantforitslunchtimeopening. Hersecurityteamhasbeenseenwaitingnearbyinalargecarorsittingonbenches70theFirstDaughterdealswithtourists'meals.
WarmweatherbroughtbyElNinohashadmixedeffectsonanimalsinusuallysnowyplacesinNorthAmericaincludingNewEnglandaccordingtoanAssociatedPressarticle. Someanimalsseemtobenefitfromhavingachancetogathermorefoodbeforewinterandfromexpendinglessenergyindailysurvivalmode.Otherslikesnowshoeharesareputatcenterstageinpredators'捕食者viewwhentheylacksnowfordisguisingtheirwhitefur﹣notagodthingforthemofcourse. Blackbearsontheotherhandhavebeenkeepingbusygatheringnutsandappleswhentheywouldnormallyhavesettledintotheirwinterhomesbynow.VermontandMassachusettsofficialshaveaskedresidentstowaittillsnowfallstotakeouttheirbirdfeedersforthesakeofsafetythearticlesaid. Wesuggestwaitingfor6ormoreinchesofsnowthatlastsbeforetakingoutyourbirdfeedersespeciallyifyouhavebeenvisitedinthepastbybearsoriftherearesightingsofbearsinyourneighborhoodForrestHammondVermontFishandWildlife'sbearbiologistsaidinthearticle.Duetolackofsnowandfrozengroundbirdsareabletoseekfoodinfieldsandforestsfortheirnaturalfoods. Snowamountscanalsodeterminehowcomfortablebearsareandhowquicklytheyconsumetheiraccumulatedfatduringhibernation冬眠notedHammondinthearticle.Thisisbecausesnowcoversandtrapsthemintheirwinterhomesandalsohidesthemfrompredators. 28.WhatmayupsetsnowshoeharesbecauseofElNino? A.Theirbeingcaughtmoreeasily. B.Theirfailingtogathermorefood. C.Theirconsumingmoreenergy. D.Theirlosingsightoftheirenemies. 29.Whydidtheofficialsaskpeopletokeepbirdfeedersuntilsnowfalls? A.Theymanydisturbbears. B.There'snoneedtodoso. C.Toavoidattractingbears. D.Forthesafetyofbears. 30.Whatdothebearbiologist'swordsimply? A.Aheavysnowisontheway. B.Bearsarecommonnowadays. C.Bearslivemainlyonbirdsinwinter. D.Warmweatherbenefitsbirdsinwinter. 31.Whichofthefollowingisthepropertitleforthepassage? A.WarmWeatherHelpsAnimalsSurvive B.SnowAmountsDetermineAnimals'WinterLife C.MeasuresShouldBeTakenToProtectWildlife D.LackofSnowAffectsNorthAmericanAnimals.
已知反应A+3B⇌2C+D在某段时间内以A的浓度变化表示的化学反应速度为1mol•L﹣1•min﹣1则此段时间内以C的浓度变化表示的化学反应速率为
Peoplelieallthetimebutdependingonhowskilledtheyare.Itcanbedifficulttodeterminewhensomeoneislyingtoyou.Doyouknowhowtorecognizethesignsthatsomeoneislyingtoyou?36 1.Liarsmakefalseeyecontact. Apersonwhoislyingtoyouwon'tmakeeyecontactwithyouortheymaketoomucheyecontact.Ifapersonislyinghemayfeelyouarewatchinghimandhewilllookdownatthefloororawayfromyoureyes.Somepeopletrytostareatyouinthefaceinadeliberateway.37 2.Liarsavoidusingcontractions缩略语 TheliarswillsayIdidNOTnoticeyourmoneyinsteadofIdidn'tnoticeyourmoney.Thisisanattemptbytheliarstobeabsolutelyclearwhattheymean.38 3.WeirdStrangeBodyLanguage. Liarsoftenfeeluneasyturnawayfromthepersontowhomtheyarespeakingblinkrapidlysmilelessandhavepitchchangesintheirtoneofvoice.Theymaycrosstheirarmswhichisasignofbeingclosedortryingnottorevealtoomuchinformation.39.Theycouldtouchpartsoftheirfaceanearoranoseorplaywithkeysoranotheritemthattheyhaveintheirhand. 4.Liarsprovideadditionalinformationwithoutbeingaskedforit. 40.Theresultisthemorecomplicatedthestoryisthelessbelievableitwillbe.Youwillhavethefeelingthatnothingcouldbefurtherfromthetruth. A.Usuallyitendsupmakingthestoryalotlessbelievable. B.Herearesomeeasywaystohelpyourecognizeliarsandcatchlies. C.Sometimespeoplewilllookunnaturalwhentheyarelying. D.Theywillgetangryifyoudoubttheirstory. E.Theyseemtothinkthatbytellingtheirstoryindetailyouwillfinditmorebelievable. F.Theytrytochangethesubjectormovetheconversationinadifferentdirection. G.Inthiswaytheyfeellikemakingeyecontactwillmakewhattheyaresayingmorebelievable.
在竖直向上的匀强电场中有两个质量相等带异种电荷的小球AB均可视为质点处在同一水平面上现将两球以相同的水平速度v0向右抛出最后落在水平地面上运动轨迹如图所示两球之间的静电力和空气阻力均不考虑则
在一定温度下的恒容密闭容器中能说明反应X2g+Y2g⇌2XYg已达到平衡的是
假设你是李华尽管你很努力但在最近的英语考试中又不及格你很烦恼父母和老师对此也有些担心.请给你的英国笔友Tom写一封电子邮件告诉他你的情况并向他求助如何学好英语.邮件要点如下 1.向Tom倾诉你的烦恼 2.请教他如何学好英语. 注意 1.词数100左右 2.可以适当增加细节以使行文连贯 3.开头和结尾已为你写好不计入总词数. DearTom Howareyou? Iamlookingforwardtoyourreply. Yours LiHua.
如图所示电路中a点电势为3Vb点接地电阻R1R2＝15电容器电容C为3pF开始时ap相接电路处于稳定状态．现在断开ap连接bp直至电路重新稳定则在这一过程中
假定英语课上老师要求同桌之间交换修改作文请你修改同桌写的以下作文.文中共有10处语言错误每句中最多有两处.每处错误仅涉及一个单词的增加删除或修改. 增加在缺词处加一个漏字符号∧并在其下面写出该加的词. 删减把多余的词用斜线\划掉. 修改在错词下面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. LastFridayourschoolorganizedustoafirestationwhatwehadexpectedforseveralday.Whenwegottherethefire﹣fighterswelcomedusbutledusintoanexhibitionhall.Thereoneofthemdeliveredthelectureonfirecontroltous.Afterthattheyshowushowtooperateafireextinguisherandevengaveourchancestopractiseusingit.NowIdaresayIcanuseitskillful!Onourwayhomewecouldn'thelptotalkingaboutwhatwehadexperienced.Wefeltveryhappyandexcitedbecausewehadgainedsomanyknowledgeaboutfirecontrolandknownwhattodoanemergency.
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InformationOverload Inmodernsocietyifwe'retryingtomakeadecisionweoftenhavesomuchinformationthatwegetconfusedandwedon'tknowwhattodo.Thisstateisknownasinformationoverload.36Itcancausestressfrustrationandreducedproductivity.Butwhatcanwedointhefaceofinformationoverload? •Planforonlyonetimeeachdaytochecke﹣mailsocialmessagingsiteschatroomsetc.Don'tallowyourselftocheckmultipletimesunlessyoutrulyarewaitingforanimportante﹣mail.37Andthateatsupyourvaluabletimebeforegettingaway. •Ifyouaresufferingfromtoomanyelectronicinterruptionsduringtheweekdayaskpeopletocallortextyouduringworkhoursonlyifit'sreallyanemergency.38 •Remindyourselfthatit'sokaytonotknoweverything.Infactit'simpossibletokeepupwiththepaceoftheinformationsuperhighway.Thesooneryouacceptthatthehappieryou'llbe.39Itisgoodtofallbehindontheinformationthatreallyisn'tworthyourattention. •40Setasidearegulartimeeachweekwhereyouandotherfamilymembersdonotuseanykindofelectronicmediatechnologiesincludingtelevision.Itcouldbesomethingyoudoeveryweekendorperhapsanhourortwoeveryevening. A.Justcatchupwiththehappiestmoment. B.Knowwhat'sworthknowingandwhatisn't. C.Almosteveryonesuffersfromittosomedegree. D.Spendtimewithyourfamilyfreefromelectronicproducts. E.Weneedtofindsomeeffectivewaystoprocesstheinformation. F.Eachtimeyougoonlineyouruntheriskofbeingaddictedtoit. G.Otherwisetheyandyouendupstealingtimefromyouremployer.
Abalanceddietmeansthenutritionofthreemealsinadayshouldbebalancedandbreakfastisveryimportanttoachievethatgoal.Skippingbreakfast61causedamagetohealthapartfromreducingworkperformance.62studyhaveshowedthatifapersondoesnoteatbreakfast63regularheorshewillbe64ahigherriskofvariousdiseases. Howevermanypeopledonoteatbreakfast.Arecentsurveyshowsthat8.6percentofpeopledonoteatbreakfasteveryday.Thesituationiseven65badinpoverty﹣strickenareas. Whilemostpeopleareusedto66eatbreakfastthequalityoftheirmealisinquestion.About25percentofpeopledonoteatahomemadebreakfast67morethan80percentofpeopledonotconsumeahealthybreakfast. Childrenwomenandpeoplelivinginpoverty﹣strickenareasaremostlikelytobeaffected68itcomestoeatingunhealthybreakfasts.Howeveroldpeople69ageabove60tendtohavehealthybreakfastbecausethisgroupmostlyretiredhavetimeand70patienttocookbreakfastthemselves.
Inagrarian农业的pre﹣industrialEuropeyou'dwanttowakeupearlystartworkingwiththesunrisehaveabreaktohavethelargestmealandthenyou'dgobacktoworksaysKenAlbalaaprofessorofhistoryattheUniversityofthePacific.Laterat5or6you'dhaveasmallersupper. Thiscomfortablecycleinwhichtherhythmsofthedayhelpedshapetherhythmsofthemealsgaverisetothecustomofthelargemiddaymealeatenwiththeextendedfamily.MealsarethefoundationofthefamilysaysCaroleCounibanaprofessoratMillersvilleUniversityinPennsylvaniasotherewasaveryimportantinterconnectionbetweeneatingtogetherandstrengtheningfamilyties. Sinceindustrializationmaintainingsuchaslowculturalmetabolismhasbeenmuchharderwiththelongmiddaymealshrinkingtowhatevercouldbestuffedintoalunchbucketorboughtatafoodstand.Certainlytherewerebenefits.Moderntechniquesforproducingandshippingfoodledtogreatervarietyandquantityincludingatremendousincreaseintheamountofanimalproteinanddairyproductsavailablemakingusmoreenergeticthanourancestors. Yetplentyhasbeenlosttooeveninculturesthatstilllivetoeat.TakeItaly.It'snosecretthattheMediterraneandietishealthybutitwasalsoajoytoprepareandeat.ItalianssaysCounihantraditionallybeganthedaywithasmallmeal.Thebigmealcameataround1p.m.Inbetweenthemiddaymealandalatesmallerdinnercameasmallsnack.Todaywhentimezoneshavelessandlessmeaningthereislittletoleranceforoffices'closingforlunchandworseningtrafficincitiesmeansworkerscan'tmakeithomeandbackfastenoughanyway.Sotheformerlysmallsupperaftersundownbecomesthebigmealofthedaytheonlyoneatwhichthefamilyhasachancetogettogether.TheeveningmealcarriesthefullburdenthatusedtobespreadovertwomealssaysCounihan. 24.WhatdoesProfessorCaroleCounihansayaboutpre﹣industrialEuropeanfamilieseatingmealstogether? A.Itwashelpfultomaintaininganation'stradition. B.Itbroughtfamilymembersclosertoeachother. C.Itwascharacteristicoftheagrarianculture. D.Itenabledfamiliestosavealotofmoney. 25.WhatdoesculturalmetabolismLine1Para.3referto? A.Evolutionaryadaptation. B.Changesinlifestyle. C.Socialprogress. D.Paceoflife. 26.Whatdoestheauthorthinkofthefoodpeopleeattoday? A.Itsqualityisusuallyguaranteed. B.Itisvariedabundantandnutritious. C.Itismorecostlythanwhatourancestorsate. D.Itsproductiondependstoomuchontechnology. 27.WhatdoestheauthorsayaboutItaliansoftheolddays? A.Theyenjoyedcookingaswellaseating. B.Theyateabigdinnerlateintheevening. C.Theyatethreemealsregularlyeveryday. D.Theywereexpertatcookingmeals.
用如图所示的装置可验证机械能守恒定律直径为d的摆球A拴在长为L的不可伸长的轻绳一端L＞＞d绳的另一端固定在O点O点正下方摆球重心经过的位置固定光电门B．现将摆球拉起使绳偏离竖直方向θ角时由静止开始释放摆球当其通过最低位置时光电门B记录的遮光时间为t． 1摆球通过最低点的速度v＝用题中字母表示 2写出满足机械能守恒的表达式用题中字母表示
Longschoolholidayshelpstudentscleartheirheadsrelaxalittleandstretchtheirbrainsindifferentways. Traditionallyschoolingscheduleshavelongbeenbasedmoreontheneedsofsocietythanonefficienteducationstrategies.ForinstanceinIcelanditwastraditionallyarrangedtoallowchildrentohelpoutwithharvest.Othercountrieshavelongsummervacationsbecauseitissimplytoohottostudy.Inotherareaswherereligionplaysanimportantroleintheholidayseasonthereligioncalendarthencallsforthebreaksothatstudentscanhaveampletimetoparticipateinthereligiousceremoniesandtraditionsofseasonalholidays. Therearesomeobviousadvantagestoavacationthatlastslonger.Familieswholivealongdistancefromrelativesareabletotraveltogethersometimesacrosstheoceaninordertoconnectwiththeirlovedones.Evenifthereisnovisitingfamilyfarawayalongholidayisagreatopportunityforkidstointeractwiththecommunity.Fromaneducationalpointofviewachildthatisabletoexperienceanotherculturecangainvaluablelanguagehistoryandsocialskills. Longschoolholidaysarealsoneededinschoolsthathavebecomeoverlyacademicandtooexam﹣focusedinrecentyearswhichrequiresaconsiderablylongerholidaybreakfromsuchamarathonpumping灌输ofknowledgeanditmakesgreatsense! GreatpsychologistslikeFreudandPiagethavestressedplay'scentralroleintheformationoffully﹣rounded全面发展的individualssothelongholidayachievesthisbyallowingstudentstoexploretheworldoutsideschool.Thestudentsgettoparticipateinactivitiesthatwouldbedifficulttododuringaregularschoolterm. Asaconsequencelongschoolholidaycanbequiteconstructivetoourstudents! 28.Whattraditionallydeterminesthearrangementofschoolholidays? A.Localneeds. B.Culturalactivities. C.Religiouscustoms. D.Academicperformance. 29.Whichisoneoftheadvantagesoflongholidays? A.Studentsrunawayfromexams. B.Childrencanlearnscienceandhistory. C.Fewercoursesarerequiredatschool. D.Familybondsarestrengthened. 30.FreudandPiagetmayprobablyagreethat. A.schoolsneedlongerholidays B.holidayactivitiesarenecessary C.playismoreimportantthanlearning D.studentsshouldtravelaroundtheworld 31.Whatisthebesttitleofthepassage? A.TraditionalSchoolHolidays B.ActivitiesforLongHolidays C.BenefitsofLongHolidays D.AdvicefromPsychologists.
一列波沿x轴正向传播t＝0时刻的波形如图所示其中EF两点相对平衡位置的位移相同从该时刻起E质点回到平衡位置的最短时间为0.05s．F质点回到平衡位置的最短时间为0.15s质点的振幅为A＝10cm则下列说法正确的是
按照氢原子的能级图下列说法正确的是
如图是磁流体发电机的示意图在间距为d的平行金属板AC间存在磁感应强度为B方向垂直纸面向外的匀强磁场两金属板通过导线与滑动变阻器相连变阻器接入电路的电阻为R．等离子体连续以速度v平行于两金属板垂直射入磁场理想电流表A的读数为I发电机内阻为r则
①②③④四种金属片两两相连浸入稀硫酸中都可组成原电池①②相连时外电路电流从②流向①①③相连时③为正极②④相连时②上有气泡逸出③④相连时③的质量减少．据此判断这四种金属活动性由强到弱的顺序是
下列说法中不正确的是 ①质子数相同的微粒一定是同种元素 ②同位素的化学性质基本相同 ③质子数相同电子数也相同的两种微粒不可能是一种分子和一种离子 ④电子数相同的微粒不一定是同一种原子 ⑤某种元素的相对原子质量取整数就是其质量数．
下列各图中表示正反应是吸热反应的图是
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