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张师傅要把一根圆柱形木料（如右图）削成一个圆锥．（1）削成的圆锥的体积最大是多少立方分米？（2）请你提出一个数学问题并解答．
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把一个圆柱形的木料削成一个最大的圆锥削去的部分是这个圆柱的．
张师傅要把一根圆柱形木料如右图削成一个圆锥削成的圆锥的体积最大是多少立方分米
把一个圆柱形木料削成一个最大的圆锥削去了2.4dm3削成的圆锥的体积是．
张师傅要把一根圆柱形木料如右图削成一个圆锥削成的圆锥的体积最大是多少立方分米
1.5分把一段圆柱形的木料削成一个体积最大的圆锥削去部分的体积是圆锥体积的
3倍
2倍
一段圆柱形木料削成一个最大的圆锥削去的体积是削成的圆锥体积的2倍．．判断对错
一段体积是52.8立方分米的圆柱形木料切削成一个最大的圆锥削去部分的体积是．
李明有一根圆柱形的铅笔头如果用削笔刀削成一个最大的圆锥圆锥的体积与削去的部分体积比你知道吗是
1：2
1：3
3：1
2：3
把一根圆柱形木料削成一个最大的圆锥体削去部分体积是圆锥体积的是圆柱体积的．
张师傅要把一个圆柱形木料削成一个圆锥木料的底面周长是18.84分米高是3米削成的最大圆锥的体积是多少
张师傅要把一根圆柱形木料削成一个圆锥木料的底面直径是4分米高是3分米削成的最大圆锥的体积是多少立方
张师傅要把一根圆柱形木料如下图削成一个圆锥．削成的圆锥的体积最大是立方分米
把一段圆柱形木料削成一个最大的圆锥体削去部分的体积是圆锥体的．
把一个圆柱形的木料削成一个最大的圆锥后体积减少18立方分米原来木料的体积是立方分米．
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张师傅要把一根圆柱形木料削成一个圆锥木料的底面直径是2分米高是3分米削成的最大圆锥的体积是多少立方
把一根圆柱形木料削成一个最大的圆锥已知削去的体积是26m3则圆柱形木料的体积是m3削成的圆锥的体积
张师傅要把一根圆柱形木料如图削成一个圆锥削成的圆锥的体积最大是多少立方分米
一个圆柱形木料要削成一个最大的圆锥则圆锥与圆柱的体积比是
3：1
1：3
3
把一个圆柱形木料削成一个最大的圆锥削掉的体积是圆柱体积的．．判断对错
张师傅要把一根圆柱形木料削成一个圆锥木料的底面直径是2分米高是3分米削成的最大圆锥的体积是多少立方分
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TheNationalFootballLeagueNFLisaprofessionalAmericanfootballleaguewith32teamsin.Howdoesonechoosewhichteamtosupport?Somepeoplechoosetheteamoftheirhometownorwheretheynowliveortheteamthattheirparentsortheirparentsortheirfriendsfollow. AboystudentfromOklahomawrotealettertoeachoftheownersorpresidentsofthe32NFLteams.Hewouldseewhatanswershegotandthenchoosehisteam. Billwashomefromschoolsick.ItwastheweekbeforeChristmas.Hewaskindofboredandneededsomethingtodo.Soheaskedhisparentsifhecouldwritetoeveryprofessionalfootballteam.Billwrotethe32lettersbyhand. Weweren'tquitesurewhatwecouldgetback.Hedidn'treallyhaveoneteamthathewantedtohearfromhismothersaidHejustwantedtoseewhatkindofreplyhe'dget. AlettertotheCarolinaPanthers'ownerJerryRichardsonwasoneofthoseposted.BillwroteinhisletterMyfamilyandIlovefootball.Theyarefansofdifferentteams.ButIdon'thaveateamtocheerforyet.IamreadytopickanNFLteamtocheeronforlifetime! AfewweekslaterBill'smotherwaspullingintoherdrivewaywhenadeliverymanarrivedwithaboxfromthePanthers.WhenBillcamehomeheexcitedlyopenedthebox.InsidehefoundasignedCarolinaPanthershelmet头盔aswellasahandwrittennotefromJerry. TheteamownerhadwrittentoBillWeshouldbehonored光荣的ifourCarolinaPanthersbecameyourteam.Wewouldmakeyouproudofyourjoiningus. Billwasoverjoyedwithwhathegot.HedecidedthatfromthenonhewouldsupportthePanthers.HekeepstheletterfromJerryinhisbedroom.HismothersaysIt'snotthehelmettheysentus.It'swhattheytoldus.ThatiswhatmatteredtoBillandwhyhechosetobecomeaPanthers'fan. 1Welearnfromthepassage. A.friendsalwayschoosedifferentteamstosupport. B.only32citiesinAmericahavetheirownfootballteams C.somepeoplechooseateamtosupportastheirparentsdo D.footballteamsarejustpopularwiththepeopleoftheirhometowns 2Billwantedtochooseafootballteamtosupportbecause. A.NFLwasveryprofessional B.hehimselfwaswillingtodoit C.hisparentsexpectedhimtodoit D.hewasillandfeltboredatschool 3TheresultofBill'slettertothePantherswasthat. A.hismotherkeptthereplyfromhim B.hegotmanyhelmetsfrom32teams C.eachteamwantedhimtobeitsplayer D.hebecameafanoftheCarolinaPanthers 4It'sclearthat. A.itispropertobeafootballfanbyChristmas B.theteamownerwrotebacktoBillbyemail C.thenotefromtheteamownermeantalottoBill D.Bill'sparentswouldalsobefansofthePanthers 5Thebesttitleforthepassagecanbe. A.ChristmasGift B.HelpfulMother C.ReceivingaHelmet D.ChoosingaTeam
Fearanditscompanionpainaretwoofthemostusefulthingsthatmanandanimalspossessiftheyareused.Iffiredidn'thurtwhenitburnedchildrenwouldplaywithituntiltheirhandswereburnedaway.Similarlyifpainexistedbutfeardidn'tachildcouldburnitselfagainandagainbecausefearwouldnotwarnittokeepawayfromthefirethathadburntitbefore.Areallyfearlesssoldier﹣andsomedoexist﹣isnotagoodsoldierbecauseheissoonkilledandadeadsoldierisofnousetohisarmy.Fearandpainarethereforetwoguardswithoutwhichmanandanimalsmightsoondieout. Inourfirstsentencewesuggestedthatfearoughttobeproperlyused.Ifforexampleyounevergooutofyourhousebecauseofthedangerofbeingknockeddownandkilledinthestreetbyacaryouarelettingfearruleyoutoomuch.Theimportantthingisnottoletfearruleyoubutinsteadtousefearasyourservantandguide.Fearwillwarnyouofdangersthenyouhavetodecidewhatactiontotake. Inmanycasesyoucantakequickandsuccessfulactiontoavoidthedanger.Forexampleyouseeacarcomingstraighttowardsyoufearwarnsyouyoujumpoutofthewayandalliswell. Insomecaseshoweveryoudecidethatthereisnothingthatyoucandotoavoidthedanger.Forexampleyoucannotpreventanairplanecrashingintoyourhouseandyoumaynotwanttogoandliveinadesertwheretherearenoairplanes.Inthiscasefearhasgivenyouitswarningyouhaveexamineditanddecidedonyourcourseofactionsofearoftheparticulardangerisnolongerofanyusetoyouandyouhavetotrytoovercomeit. 1Whywouldchildrenplaywithfirerepeatedlyeveniftheyhadbeenburnedbefore? A.Theyhadnofearoffire. B.Theywerenotwelleducated. C.Theyhadnosenseofpain. D.Theywantedtobefearlesssoldiers. 2HowdoyouunderstandtheunderlinedpartinParagraph2? A.Youmustkeepcalminfaceofdanger. B.Youneedsomeonetoserveyouathome. C.You'dbetterstayinthehouseinfearofdeath. D.Youshouldn'tbecontrolledbutservedbyfear. 3Whatcanweinferfromthetext? A.Fearisalwayssomethinghelpful. B.Toomuchfearisusuallyharmful. C.Fearissomethingthatcanbeavoided. D.Fearshouldbeusedasourguideinlife. 4Thebesttitleforthispassageshouldbe. A.TheValueofFear B.PainandActions C.NoPainsNoGains D.WaystoAvoidDanger
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Ofcourseshewasn'treallymyauntandoutoffearInevercalledherthattoherface.IonlyreferredtoherasMyAuntFanniebecausethenamealwaysmademyfatherlaughquietlyandgavemymothercausetolookstrictlyatbothofus﹣atmeforbeingdisrespectfulofmyelderandatmyfatherforencouragingmybadbehavior.IenjoyedbothreactionssoIlookedforeveryopportunitytoworkthenameintoasmanyconversationsaspossible. AsayoungwomanmymotherhadworkedinthekitchenofalargeVictorianfarmhouse.DuringthoseyearsmymotherhelpedAuntFannymakethebestblueberryjamevertastedbyanyoneinGlenfield.Shewaswell﹣knownforherjamandforneversharingtherecipewithothers.EventhoughmymotherknewtherecipebyheartaslongasAuntFanniewasaliveshenevermadethejamwithoutAuntFannieinourkitchentodirecttheprocessandkeepthesecret. EachAugustmymotherwouldpreparemeforAuntFannie'svisit.OneyearafterIhadhelpedwiththejamprocessAuntFanniegavemeacoinandthenmademepromisethatIwouldneverspendit.Holdontothiscoinshesaidandsomedayyouwillberich.Istillhavemyveryfirstcoingiventomebymygrandmother.SoIkeptthecoininasmallboxandwaitedtobecomerich. InowhavetheblueberryjamrecipeandthecoinfromAuntFannie.Inpeople'seyesAuntFannie'ssuccessresultedfromthatsecretrecipe.Buttomeitwasjustacommonrecipe.NeitherhavemademebecomearichpersonbutIkeepthemasreminderstoholdontothevaluablethingsinlife.Moneycanmakeyoufeelrichforawhilebutitistherelationshipsandthememoriesoftimespentwithfriendsandfamilythattrulyleaveyouwealthy.Andthatisafortunethatanyonecanbuild. 1WhydidtheauthoralwaysusethenameMyAuntFannieinconversations? A.ShelikedAuntFannie'srecipe. B.ShewasfrightenedofAuntFannie. C.Sheenjoyedherparents'reactions. D.ShegreatlyrespectedAuntFannie. 2TheunderlinedwordsheinParagraph2refersto. A.AuntFannie B.theauthor'sgrandmother C.theauthor'smother D.AuntFannie'sgrandmother 3Inthelastparagraphtheauthorencouragesreadersto. A.holdontothefirstcoininlife B.makeasmanyfriendsaspossible C.makemoneywiththeirownhands D.spendmoretimewithfamilyandfriends 4Whatcouldbethebesttitleforthispassage? A.TheKeytoSuccess B.BlueberryJamRecipe C.AFortuneBuiltfromaCoin D.ARelationshipofTrust
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AfewyearsagomyhusbandandIwereonanislandforaweekwithourtwolittledaughters.Aswetalkedaboutwhattodonextourdaughtersjumpedinandtoldusexactlywhattheywantedtodo.Weagreed. AssoonaswewalkedintothemainareaofButterflyMuseumwesawthousandsofbeautifulbutterflies.Theyallflewwiththeircolorfulwings.Mygirlswerejumpingupanddown.AndIknewwehadmadetherightdecisiontocometothemuseum.Theywerehavingsomuchfun. IturnedtoourguideandaskedcuriouslyHowlongdobutterflieslive?shesaidAbouttendays. Whatcanbutterfliesdointendays? TheguidestoppedlookedatmeandsaidTheymaketheworldamorebeautifulplace. AfterwesaidgoodbyeIcouldn'tstopthinkingaboutwhattheguidehadsaid.Shewasright.Weallhavesomethingtooffertheworld.Ifweallspendtimedoingwhatwecandoforotherswecanmaketheworldabetterplace. 1Whatdidthegirlswanttodo? A.Gotovisitanisland. B.VisitButterflyMuseum. C.Listentotheguide. D.Maketheworldbeautiful. 2Whatmadethewriterthinktheyhadmadetherightdecision? A.Theywerewelcomeinthemuseum. B.Shesawthousandsofbeautifulbutterflies. C.Herdaughterswerehavingagoodtime. D.Sheknewhowlongbutterflieslived. 3Theunderlinewordcuriouslymeans. A.害怕地 B.自豪地 C.好奇地 D.愤怒地 4Howcanwemaketheworldabetterplace? A.Byvisitingsomemuseums. B.Bytalkingwithaguide. C.Bylivingahappyandhealthylife. D.Bydoingwhatwecandoforothers. 5Whichisthepropertimeorder顺序ofwhathappened? a.ThegirlsenjoyedthemselvesinButterflyMuseum. b.MyhusbandandItalkedaboutwhattodonext. c.Theguidetoldmehowthebutterfliesspenttheirlife. d.Ikeptthinkingabouttheguide'swords. A.b→a→c→d B.a→b→d→c C.a→d→b→c D.a→b→c→d
TimJeffdoyoupreferworkinginagrouporworkingalone? JeffI'mgoodat1workbymyselfbecauseifIamdoingsomethingIlikeIcangetit2doquickly.3ifIamworkingwithateamwherepeopleallwanttodoagoodjobIthink4teamisfun. TimDoyoupreferworkingwearingauniformorputtingwhateveryouwant? JeffIthink5youwearauniformsometimesyougetrespect. TimSohowaboutaworkingschedule?Wouldyoupreferasettimejob? JeffNo.Ithink6isdifficulttodoasettimejob.LastyearI7producefurnitureinafactory.EverymorningIhadtogetupatsix.WhenIgothome8workitwasalmosteight. TimYou9beverytired.Bythewaydoyoupreferbeingpaidbythehourordoyouprefersalary? JeffIthinksalarymaybea10goodwaytogothanbeingpaidbythehour.
Hepublishedanew系列ofarticlesforstudentsofEnglish.
Iranintoastrangerashepassedby.Ohexcusemepleasewasmy1.HesaidPleaseexcusemetooIwasn'twatchingforyou.Wewerevery2thisstrangerandI.Wewentonourwayandwesaidgoodbye.Butathomea3storyistold. LaterthatdaywhenIwascookingtheeveningmealmydaughterstoodbesidemevery4.WhenI5Inearlyknockedherdown.Moveoutofthe6Isaidwithafrown.Shewalkedawayherlittleheartbroken.Ididn't7howharshly严厉地I'dspoken. WhileIlayawakeinbedthateveningmyhusbandsaidtomeWhile8astrangeryouarepolitebutwiththegirlyouloveyouare9.Gotolookonthekitchenflooryou'llfindsomeflowersbythedoor.Thosearetheflowersshebroughtto10.Shepickedthemherselfpinkyellowandblue.Shestoodquietlynotto11thesurpriseandyou12sawthetearsinhereyes. 13mytearsbegantofall.Iquietlywentandkneltdownbyherbed.WakeuplittlegirlIsaid.Aretheseflowersyoupickedforme?ShesmiledIfoundthemoutbythetree.Ipickedthem14they'reprettylikeyou.Iknewyou'dlikethemespeciallytheblue. IsaidDaughterI'msorryforthewayI15today.I16haveyelledatyouthatway. ShesaidOhMomthat'sokay.Iloveyouanyway. IsaidDaughterIloveyoutoo.AndIdoliketheflowersespeciallytheblue. Ihadgottheworld17again.I'd18tobepolitetopeopleinthestreet﹣good19makesocietywork.Butastrangerissomeonewebumpintoonceandthenneverseeagain﹣and20isforlife. 1A.answer B.words C.reply D.speech 2A.careful B.polite C.serious D.unhappy 3A.interesting B.meaningful C.similar D.different 4A.still B.noisy C.upset D.excited 5A.called B.turned C.returned D.removed 6A.house B.space C.way D.area 7A.realize B.care C.prove D.understand 8A.referringto B.listeningto C.dealingwith D.pickingup 9A.anxious B.patient C.disappointed D.unkind 10A.us B.you C.thefamily D.herfriends 11A.ruin B.expect C.announce D.handle 12A.seldom B.simply C.even D.never 13A.Bythistime B.Atonetime C.Foratime D.Atthesametime 14A.while B.so C.unless D.because 15A.considered B.acted C.developed D.performed 16A.shouldn't B.couldn't C.wouldn't D.mustn't 17A.clear B.right C.beautiful D.meaningful 18A.begin B.learn C.continue D.change 19A.manners B.habits C.lifestyle D.behaviors 20A.lover B.companion C.family D.friend
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Dr.Johnsonand1havebeentryingtobuildhimup体格上.
Suchadietiswidelybelievedtooffer保护againstanumberofcancers.
随着科幻电影流浪地球的热映“引力弹弓效应”进入了公众的视野．“引力弹弓效应”是指在太空运动的探测器借助行星的引力来改变自己的速度．为了分析这个过程可以提出以下两种模式探测器分别从行星运动的反方向或同方向接近行星分别因相互作用改变了速度．如图所示以太阳为参考系设行星运动的速度为μ探测器的初速度大小为v0在图示的两种情况下探测器在远离行星后速度大小分别为v1和v2．探测器和行星虽然没有发生直接的碰撞但是在行星的运动方向上其运动规律可以与两个质量不同的钢球在同一条直线上发生的弹性碰撞规律作类比．那么下列判断中正确的是
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. 删除把多余的词用斜线\划掉. 修改在错的词下画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. Questioningcanleadtosearchingforananswer.Ifweareinthehabitofaskingwhetherthatwearetoldistruewecanfindthecorrectanswerandlearnmore. TwoyearsagoourteacherMr.Alexofferedusananswerofadifficultmathprobleminclass.BecausetheanswerseemedalittlestrangenobodybutIdoubtedit.ThoughtthathissolutionmightbewrongIcarefullyanalyzedtheproblemandtrytoworkitoutinadifferentway.HalfahourlaterImanagedtofindthecorrectanswer.WhenIshowedmyanswertohertheteacherpraisedmeformyindependentlythinking. FromthisexperienceIhavebeenlearntthatquestioningcanserveasabridgehelpsustoseekthetruth.
如图甲所示两平行金属板MNPQ的板长和板间距离相等板间存在如图乙所示的随时间周期性变化的电场电场方向与两板垂直不计重力的带电粒子沿板间中线垂直电场方向源源不断地射入电场粒子射入电场时的初动能均为Ek0已知t＝0时刻射入电场的粒子刚好沿上板右边缘垂直电场方向射出电场．则
如图在xOy坐标平面第一象限内x≤1m的范围中存在以y＝x2为上边界的沿y轴正方向的匀强电场场强大小E1＝2.0×102N/C．在直线MN方程为y＝1m的上方存在方向垂直纸面向里磁感应强度为B的匀强磁场．在x＝﹣1m处有一与y轴平行的接收板PQ板两端分别位于MN直线和x轴上在第二象限MN和PQ围成的区域内存在沿x轴负方向的匀强电场场强大小为E2．现有大量的带正电粒子从x轴上0＜x≤1m的范围内同时由静止释放粒子的比荷均为＝1.6×105C/kg不计粒子的重力及其相互作用． 1求在x＝0.5m处释放的粒子射出电场E1时的速度大小 2若进入磁场的所有带电粒子均从MN上同一点离开磁场求磁感应强度B的大小 3若在第2问情况下所有带电粒子均被PQ板接收求电场强度E2的最小值和在E2最小的情况下最先打在接收板上的粒子运动的总时间．
假如你是红星中学的李明某英语报正在招募青少年英语记者你有意应聘请你根据以下提示给报社写一封自荐信. 要求 1.语言通顺意思连贯 2.词数不少于80词. 3.文章的开头和结尾已经给出不计入总词数. DearSir/Madam MynameisLiMing. I'mlookingforwardtoyourreply.Iwouldgreatlyappreciateitifyoucouldgivemethechance. Yourssincerely LiMing
某同学做了一个趣味实验如图所示有两个弹性小球AB重叠放置质量分别为m1m2两球球心在同一竖直线上．现让它们在距水平地面高h处由静止释放落地时认为小球B先与地面碰撞再与小球A碰撞小球A碰后能上升的最大高度为H．所有的碰撞都是弹性碰撞碰撞时间忽略不计碰撞前后两小球都在竖直方向运动两小球均可视为质点不计空气阻力．下列说法正确的是
如图所示倾角为θ＝37°的足够长的固定斜面上叠放着质量为M＝0.4kg的足够长的木板A和质量为m＝0.2kg的物块B可视为质点A与斜面A与B间的动摩擦因数分别为μ1＝0.25μ2＝0.75．开始时A下端与固定挡板C对齐B与C间的距离L0＝0.135m．t＝0时将A由静止释放同时B以v0＝0.9m/s的速度沿板下滑极短的可不计的时间内给B沿板向下的冲量B获得初速度v0．已知接触面间的最大静摩擦力与滑动摩擦力大小相等B与C碰撞时间极短可不计且碰撞前后B速度大小不变A与C不会接触取g＝10m/s2sin37°＝0.6cos37°＝0.8．求 1从B开始运动到与C第一次碰撞所经过的时间t1和这段时间内A运动的位移大小x1 2B第二次与C碰撞前瞬间速度大小v2和B第一次碰撞C到第二次碰撞C经历的时间t2 3从B开始运动起在t＝1.5s时间内系统产生的总热量Q．
Afteryearsofresearchandtestingthehybridcarwasdevelopedandputonthemarket.It'saninterestingandexcitingnewimprovementintoday'sworldaswelookforbetterwaystoprotectthequalityoftheairwebreatheandconserveournaturalresources. Thequalityofourairisaffectedbymanydifferentthings.Butoneofthelargestsourcesofairpollutionistheburningoffossilfuelssuchascoalandgasolinewhichisusedtopoweracar'sengine.TheEPAhassetnationalstandardstohelpcontrolthelevelofharmfulpollutantssentoffintotheairandtheautomobileindustryhasactedbyproducingahybridcarthatuseslessgasandthereforecauseslesspollution. Ahybridcarisacombinationofaregularcarthatrunsongasolineandanelectriccarthatisbatterypowered.Somepeopletendtothinkthatsincethehybridcarispartiallyelectricyouhavetoplugitintochargeit.Butthat'snothowitworks.The144voltbatterypackisactuallyrechargedthroughtheenergythatisproducedwhenthecar'sbrakesareused.Thisisreferredtoasregenerativebrakingbecauseitgenerateselectricity. Althoughthehybridcarstillrunsongasolinemostofthetimethishelpsituselessgasthanaregularcar.Whenthedriverstopsatatrafficlighttheengineautomaticallyshutsofftosavefuel.Thenassoonasthedriverputsthecaringearandtouchesthegaspedaltheenginestartsbackup. Haveyoueverriddeninacarwithsomeonewhoranoutofgas?Thatprobablywouldn'thappenifyouwereridinginahybridcar.ItflashesawarningonitscomputerscreenthatsaysIamlowongas.WhenitcompletelyrunsoutthewarningreadsYOUARENOWOUTOFGAS!Thentheelectricpowersupplykicksintoletthedrivertravelafewmoremilestoagasstation. 1Whichofthefollowingistrueaccordingtothepassage? A.Thehybridcarwillbeputonthemarket. B.Hybridcarsrunfasterthanregularcars. C.Whenthehybridcarstopsatatrafficlightthedriverwillgetawarning. D.Theburningoffossilfuelsisoneofthelargestsourcesofairpollution. 2Accordingtothepassagethewordhybridrefersto. A.ahigh﹣techdiscovery B.energysaving C.anewinvention D.acombinationoftwothings 3Regenerativebreakingisanimportantprocessofthehybridcarbecause. A.itallowsthecartocometoaquickstop B.itgivesthedriverasmootherride C.itproducesenergytochargethebattery D.itcancontrolthespeedofthecar 4WhichofthefollowingisrightabouttheEPA? A.Theydesignedhybridcars. B.Theyoutlawed宣布……为不合法theburningoffossilfuels. C.Theysetimportantguidelinesthathelpcontrolpollution. D.Theirmainpurposeistoprotectendangeredplantsandanimals. 5Whichofthefollowingisthereasonfordevelopinghybridcars? A.Theyuselessgasthanregularcars. B.They'resafertodrivethanmostcars. C.They'remoremodernthanothercars. D.Theycostlessthanregularcars.
如图所示开口向下的“┍┑”形框架两侧竖直杆光滑固定上面水平横杆中点固定一定滑轮两侧杆上套着的两滑块用轻绳绕过定滑轮相连并处于静止状态此时连接滑块A的绳与水平方向夹角为θ连接滑块B的绳与水平方向的夹角为2θ则AB两滑块的质量之比为
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