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如图所示，光滑曲面下端与光滑水平面相切，一质量为m的弹性小球P沿曲面由静止开始下滑，与一质量为km（k为大于0的正整数）且静止在水平地面上的弹性小球Q发生弹性正碰．为使二者只能发生一次碰撞，下列关于...
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如图所示A.B.两球放在光滑的水平面上水平面的右侧与竖直平面内一光滑曲面相切现给A.一向右的速度让A
如图所示光滑曲面下端与光滑水平面相切一质量为m的弹性小球P沿曲面由静止开始下滑与一质量为kmk为大
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两质量分别为和的劈A.和B.高度相同放在光滑水平面上A.和B.的倾斜面都是光滑曲面曲面下端与水平面相
如图所示光滑曲面轨道的水平出口跟停在光滑水平面上的平板小车上表面相平质量为m的小滑块从光滑轨道上某处
如图所示光滑曲面下端与光滑水平面相切一质量为m的弹性小球P沿曲面由静止开始下滑与一质量为kmk为大
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如图所示光滑曲面轨道的水平出口跟停在光滑水平面上的平板小车上表面相平质量为m的小滑块从光滑轨道上某处
10分两质量分别为M1M2的劈A.和B.高度相同彼此独立位于光滑平面的同一水平直线上A.和B.的倾斜
两质量分别为M1和M2的劈A.和B.高度相同放在光滑水平面上A.和B.的倾斜面都是光滑曲面曲面下端与
两质量均为2m的劈A.和B.高度相同放在光滑水平面上A.和B.的倾斜面都是光滑曲面曲面下端与水平面相
如图所示光滑的水平面上有一个质量为M.＝2m的凸型滑块它的左侧面与水平面相切并且光滑滑块的高度为h质
如图所示质量为M.的物块静止在光滑的水平面上物块的弧面底端与水平地面相切.一个质量为m的小物体以速度
如图所示光滑水平面上有一个静止的质量为M的小车它的上表面是由水平面连结1/4圆弧的光滑曲面组成一个质
两个质量分别为M.1和M.2的劈A.和B.高度相同放在光滑水平面上.A.和B.的倾斜面都是光滑曲面曲
如图所示光滑的水平面上有一个质量为M.=2m的凸型滑块它的一个侧面是与水平面相切的光滑曲面滑块的高度
如图所示光滑水平面上有一个质量为M=2m的凸形滑块它的左侧面与水平而相切并且光滑滑块的高度为h质量为
如图所示长为L=2m的木板A.质量为M=2kgA.静止于足够长的光滑水平面上小物块B.可视为质点静止
如图所示轻弹簧的一端固定在竖直墙上质量为m的光滑弧形槽静止放在光滑水平面上弧形槽底端与水平面相切一个
在下滑过程中，物块的机械能守恒
在下滑过程中，物块和槽的动量守恒
物块被弹簧反弹后，做匀速直线运动
物块被弹簧反弹后，能回到槽高h处
如图所示质量为M.的弧形槽静止在光滑的水平面上弧形槽的光滑弧面底端与水平地面相切一个质量为m的小物块
如图所示长为L=2m的木板A.质量为M=2kgA.静止于足够长的光滑水平面上小物块B.可视为质点静止
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为比较甲以两名篮球运动员的近期竞技状态选取这两名球员最近五场比赛的得分制成如图所示的茎叶图有以下结论 ①甲最近五场比赛得分的中位数高于乙最近五场比赛得分的中位数 ②甲最近五场比赛得分平均数低于乙最近五场比赛得分的平均数 ③从最近五场比赛的得分看乙比甲更稳定 ④从最近五场比赛的得分看甲比乙更稳定． 其中所有正确结论的编号为
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TheUnitedStatesestimatesthataboutoneoutofevery10peopleontheplanettodayisatleast60yearsold.By2050it'sprojectedtobeoneoutof5.Thismeansthatnotonlywilltherebemoreoldpeoplebuttherewillberelativelyfeweryoungpeopletosupportthem. ProfessorRichardLeeoftheUniversityofCaliforniaatBerkeleysaysthisagingoftheworldhasagreateffectoneconomics.Populationagingincreasestheconcentrationofpopulationintheolderagesandthereforeitisexpensivehesaid. Agingpopulationsconsume消耗moreandproduceless.Withmorepeoplelivinglongeritcouldgelexpensive.ButMr.Leesayswithcontinuingincreasesinworkerproductivityandwiseplanningitcanbemanageable. SocietieshavedifferentmethodsforcaringfortheelderlybuteachcarriesacostGenerallytherearethreetypesofsupportSeniorscanliveoffthewealththeygainedwhentheywereyounger.Theycanrelyontheirfamilytotakecareofthemortheycanrelyonthemovement. Inindustrializednationsgovernmentscreatedpublicly﹣funded公共资助的supportsystems.TheseworkedrelativelywelluntilrecentyearswhenagingpopulationgrowthinplacesliketheUnitedStatesandWesternEuropebegantograduallyweakenthesystems'finances资金.Thesenationsnowfacesometoughchoices.Mr.Leesaystheelderlyinsomeofthesecountriesmusteitherreceivelessmoneyretirelaterorincreasetaxestomakethesystemcontinuable. Mostdevelopingnationshaven'tbuiltthistypeofgovernment﹣fundedsupportbuthaveinsteadreliedonfamiliestocarefortheirelderly.Thesenationsalsogenerallyhaveamuchyoungerpopulationwhichmeanstheirsituationisnotasurgentasmoredevelopednations.ButMr.Leesaysthatdoesn'tmeantheycanpatnoattentiontheissue.ThirdWorldcountriesshouldgiveverycarefulthoughttothisprocesstopopulationagingandhowitmayaffecttheireconomies﹣nowbeforepopulationagingevenbecomesanproblemheexplained. 1Whatisoneofthelikelyresultsofpopulationagingaccordingtothepassage? A.Therewillbemoreoldpeoplethanyoungones. B.Morethan20%ofpeoplewillbeatleast60yearsold. C.Itwillbemoredifficulttosupportoldpeople. D.Theworld'sconcentrationwillbeonoldpeople. 2WhatdoesProfessorLeethinkoftheproblemofpopulationaging? A.Itislikelytomanageit. B.Itistooexpensivetosolveit. C.Itdependsonhowmuchtheoldgainedwhenyoung. D.Itdependsonthewealthofthewholesociety. 3Whatproblemdothepublic﹣fundedsupportsysteminindustrialnationsface? A.Theyfacetoughchoice B.Thereisnotenoughmoneytosupporttheold. C.Taxesaretoolow. D.Theirpopulationsgrowtooquickly. 4Whichofhefollowingaboutdevelopingcountriesistrue? A.Sofartheireconomieshaven'tbeengreatlyaffected. B.Theirgovernmentgivemoremoneytosupporttheold. C.Theyneedn'tpayattentiontoagingpopulation. D.Theirsituationisalsoserious.
在△ABC中角ABC的对边分别为abc已知向量＝cosBsinA﹣B向量＝2cos2﹣sinB5＝5cosB+3． 1求cosA的值 2若a＝4b＝5求向量在方向上的投影．
已知点A01B32向量＝
假设你是李华Harry是你的美国笔友.在来信中谈到他学校的图书馆.你常常去你校的图书馆.于是你回信向他介绍这个图书馆.内容包括 1.图书馆的建筑简介如面积层高位置等 2.藏书册数及图书种类. 3.服务项目图书的借阅教师及学生阅览室. 注意 1.信的开头已为你写好 2.词数100左右. 3.可以适当增加细节以使行文连贯. DearHarry Howarethingsgoingwithyou?TalkingaboutlibrariesIwouldliketointroducetoyouaboutourschoollibrary. Bestwishes Yours LiHua
在△ABC中角ABC的对边分别为abc面积为S满足2S+ab＝a+b2﹣c2则tanC＝．
ThanksgivingDayisspecialholidayintheUnitedStatesandCanada1. ThanksgivingDayisreallyaharvestfestival.Thisiswhyitiscelebratedinlatefallafterthecropsarein2.OnDecember41619thePilgrimsfromEnglandlandednearwhatisnowCharlesCityVirginia.TheykneltdownandthankedGodfortheirsafejourneyacrosstheAtlantic. 3ThePilgrimslandedatwhatisnowPlymouthMassachusettsin1620.Theyhadadifficulttimeandthefirstwinterwascruel.ManyofthePilgrimsdied.Butthenextyeartheyhadagoodharvest.SoGovernorBradforddeclaredathree﹣dayfeast盛宴.4Everyonebroughtfood. Intimeothercolonies殖民地begantocelebrateadayofthanksgiving.ButittookyearsbeforetherewasanationalThanksgivingDay.DuringtheCivilWarSarahJosephaHalepersuadedAbrahamLincolntodosomethingaboutit.5TodayAmericanscelebratethishappyharvestfestivalonthefourthThursdayinNovember.CanadianscelebrateThanksgivingDayinmuchthesamewayastheirAmericanneighbours.ButtheCanadianthanks﹣givingDayfallsonthesecondMondayinOctober. A.ButoneofthefirstthanksgivingsinAmericahadnothingtodowithagoodharvest. B.HedeclaredthelastThursdayofNovember1863asadayofthanksgiving. C.ThePilgrimswerethosewhocelebratedthefirstThanksgivingDay. D.Familiesandfriendsgathertoeatandgivethanksfortheirblessing. E.ThePilgrimsinvitedIndianfriendstojointhemfortheirspecialfeast. F.ThisiswhyhedecidedtomakeitanationalholidaythroughouttheU.S.. G.ThefirstNewEnglandThanksgivingdidcelebratearichharvest.
Bitcoinandotherso﹣calledcryptocurrencies加密货币havebeenalloverthenewslately.Apparentlytheideaofmoneythat'snottiedtoaspecificbankoraspecificcountryisappealingtomany.Andmoreandmorepeopleshowtheirinterestinthesecryptocurrencies. Inthepastmoney'smakeupvariedfromplacetoplace.Variousobjectshaveservedascurrencyincludingbeadsivoryandshells.InWestAfricabracelets手镯ofbronzeorcopperconsideredtohavegreatworthwereusedascashespeciallyifthebusinesswasassociatedwiththeslavetradethere.ThroughoutthecolonialperiodwhentobaccowasplantedgreatlyandbroughtbigeconomicbenefitsitwasusedinplaceofcoinsorpaperbillsinVirginiaMarylandandNorthCarolina. TodayonMalaitaanislandinthePacificaspecifictypeofshellstillservesascurrencyandsomepeoplethereareevenhoardingitjustlikeBitcoinconvincedthatonedayitwillmakethemwealthybeyondimagination.MaryBrunoashopownerfromthesmalltownofAukionMalaitasaidoneofdarkershellsmightgetyouabouttwocansoftuna金枪鱼butoneofredshellsmightgetenoughtunatofeedabigfamilyforalongtime.Justlikeaplacethatcreatescoinsthere'sonlyoneplaceontheislandwheretheshellswhicharepolishedandstrungtogethertoform3﹣foot﹣longropesaremade.TheredwhiteandblackshellsallcomefromLangaLangaLagoonwhereartificialislandswerebuiltbylocalstoescapefromthewarlongago.Oncetrappedontheseislandslocalsneededacurrencytouseamongthemselvesandsotheshellcurrencywasborn. Justlikecryptocurrenciestherearethosewhothinktheislandersaresmarttoinvestinthistypeofmoneywhichisreportedtohaveriseninvalueoverthelastthreedecades.Itmightseemstrangebutwhatisapileofdollars?It'sjustaspeciallyprintedpieceofpaperthatwe'veassignedvalueto﹣﹣andprobablylessdurable耐用overtimethanthoseshells. 1WhatdoestheauthorintendtotellusinParagraph1? A.Atrendofcurrency. B.People'sinterestinBitcoin. C.Banks'controlovercurrency. D.Aneffectofcryptocurrencies. 2TheunderlinedwordhoardinginParagraph3canbereplacedby. A.selling B.polishing C.collecting D.hiding 3Accordingtothispassagewhatdeterminesthevalueofshells? A.Theircolor. B.Theirshape. C.Theirsource D.Theirweight. 4Whatistheauthorsattitudetowardstheislanders'investinginshells? A.Doubtful. B.Objective. C.Uncaring. D.Approving.
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处错误每句中最多有两处.错误涉及一个单词的增加删除或修改. 增加在缺词处加一个漏词符号∧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的词. 注意1.每处错误及修改均仅限一词 2.只允许修改10处多者从第11处起不计分. LastnightourschoolorganizedanEnglishCorner.Iwenttherewithdozenofstudentsmostofthemwereseniors.AndtherewasalsonativeEnglishspeakerwhowasinvitedtocommunicatewithus.Hewasveryhumorousandeasy﹣goingbutlovedansweringquestionsraisebystudents.ItwasthefirsttimethatIhaveattendedanEnglishCorner.Ididn'taskforasinglequestionbecauseIwasreallynervousandpooratspokenEnglish.SoIjustlistenedtohertalkingwithotherstudents.IwasdeterminedtopracticingspeakingEnglishashardasIcouldhopingtocommunicatewithforeignersfluentinEnglishinthefuture.
Englishisnowthefirstlanguageofabout400millionpeoplethemotherlanguageof12countriesandtheofficiallanguageofone﹣fifthofthelandareaoftheworld1meansone2everysevenpeopleintheworldspeaksEnglish. Moreandmorepeoplehavefounditimportant3learnEnglishwellinrecentyears.InItalyforexampleEnglishisamustformanytechnicaljobs.InChinaEnglishisthe4importantforeignlanguagethatislearnedatschool. TheEnglishlanguagehasneverstoppedchanging.Italwaysborrowswordsandphrasesfromotherculturestoenlarge5itvocabulary.6actualmodemEnglishisquitedifferentfromwhat7usehundredsofyearsago. Englishissowidelyusedthatithasbecomethestandardlanguagefor8communicateinternationally.About75%oftheworld'smail9beinEnglish.About60%oftheworld'stelephonecallsaremadeinEnglishandabout60%oftheworld'sradioprogramsarebroadcastinEnglish.What'smoreoverhalfoftheworld'sbooksandmagazinesarewritteninEnglish.In10wordEnglishisnowtheworld'sfirstlanguage.
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已知函数fx＝x2+x+6存在x∈[02]使得fx≥a2﹣a成立则实数a的取值范围
一个几何体的三视图如图所示其中俯视图为正三角形则侧视图的面积为
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在△ABC中角ABC所对的边的长分别为abc若asinA+bsinB＜csinC则△ABC的形状是
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WhenAmericansKayandLarryDayfoundastoresellingkitesnearly20yearsagotheydecidedtobuyafewkitesfortheirfamily.ForfunLarryboughtoneforhimself.HewentoutandflewitanddecidedtogobackandaddmorefuntotheeventKayremembered. Sincethensheandherhusbandhavelovedkiteflying.Theyownmanykitesandplantripsaroundflyingthem.Theyalsoorganizeakite﹣flyingeventeachwinterintheirhometowninIowa.I'matpeacewhenI'mflyingakitesaidLarry. Kite﹣flyinghasalonghistoryasanactivityforadultsandchildren.Thecustomofflyingapieceofclothhighintheskybeganmorethan2000yearsagoinChina.Sincethenkiteshavebeenusedtodoscientificexperimentspowerboatstakepicturesfromtheairandmuchmore. Sometimesthebestflyingconditionshappeninwinter﹣onafrozenlakesaidKayDaywhowithherhusbandorganizestheColortheWindKiteFestival.IttakesplaceeveryFebruaryonClearLakeinIowa.Thefestivaladdscolortothewinterskyandgivespeopleareasontogooutsidesheadded.TheDaysinviteexpertflierstocomeandsharetheirloveforkiteswithlocalsandvisitors.Thisyearmorethan100childrenattendedakite﹣makingclass.Kitersareareallygoodgroupofpeople.It'safamilysaidLarry. Kaysaysthattheloveforkitescanspreadtootherseasily.ShesayshertwochildrenDylanandCardinstartedflyingkitesaboutthreeyearsagoafterattendingakitefestivaltheyheld.Theylikewatchingtheirparentsflykiteshappilytogether.Thesceneencouragesthemtoflykitesthemselves.IdoenjoyattendingkitefestivalsDylansaid.The13﹣year﹣oldboyenjoysitwhenhiskitemovesfreelythroughthesky. 1WhenLarryflewakite20yearsagohedecidedto. A.spreadhisloveforkitestohisfamily B.plantripstoflykites C.makekiteflyingmoreenjoyable D.holdakitefestival 2Whatdoesparagraph3mainlytalkabout? A.Kite﹣flyingactivitiesforkitelovers. B.Thehistoryofkites. C.Methodsofmakingakite. D.Theusageofkites. 3FromLarry'spointofviewthekitefestivalcan. A.attractmanyexpertsfliers B.maketheirhometownfamous C.bringpeoplemuchfreedom D.strengthenhumanrelations 4Whatcanbeinferredfromthelastparagraph? A.Childrenaregoodatflyingkites. B.Peopleofallagesloveflyingkites. C.Parents'interestscaninfluencetheirkids. D.Parents'skillsshouldbepassedontokids.
已知函数fx＝ab∈R． 1若关于x的不等式2ax﹣b＞0的解集为求fx＜0解集 2若a＝解不等式fx＞0的解集．
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已知m∈R直线lmx﹣2+2y＝0恒过定点P则P的坐标为．
已知等比数列{an}__比q＝2a4是a3+2a5﹣6的等差中项． 1求数列{an}的通项公式 2求数列{an}的前n项和Sn．
WhenIwasfifteenyearsoldItoldmymotherIwantedcontactlenses隐形眼镜.Somegirlsatmyschoolhadgotthemandtheylooked1withouttheirglasses.MomtoldmethatIwouldhavetogetan2topayforthelensesmyself.When3herthatthelegalworkingagewassixteenshesaidthatshewouldaskherformer4ofagrocerystoretohiremeparttime.Shesaidthatshewasgreatly5andencouragedbyhimwhensheworkedthere. Ihad6earnedmoneybybabysittingrunningerrandsandshovelingsnow.Sothiswasmyfirstexperienceofworkingwithadults.OnmyfirstdayI7groceries.Everyitemhadtobeplacedtidilyinbrownpaperbags.EventuallyIwasgiventhe8ofrunningthesnackbar.Mydutymainly9makinghotdogsofferingsupplieslikefreshdonutsandpastriesand10customers.AsittookaboutanhourforthehotdoggrilltocooldownafterIshutitoffIwasusually11employeetoleavethestore.Iwasvery12incheckingmyworkareatoensurethat13wascleanandtheelectronicswere14beforeIwenthome.IlovedmyworktheresoI15workingatthegrocerystorethroughouthighschool. Thisexperiencefinallynotonlyhelpedmegetmycontactlensesbutalso16memanythings.Workingwithadultsgavemean17oftheirdailystrugglesandthe18ofbeingawifeandmotherwhileworkingfulltime.WhenIwasatworkIwas19likeanadultsoIhadtoworkhardformypaycheck.NowwhenIgoshoppingatgrocerystoresIespecially20theemployeesthere. 1A.morespecial B.moreintelligent C.prettier D.brighter 2A.chance B.approval C.plan D.job 3A.reminded B.persuaded C.warned D.reported 4A.student B.colleague C.boss D.relative 5A.blamed B.educated C.moved D.supported 6A.mainly B.previously C.fairly D.exactly 7A.checked B.counted C.bagged D.purchased 8A.present B.reward C.benefit D.responsibility 9A.deserved B.occupied C.involved D.devoted 10A.serving B.controlling C.finding D.pleasing 11A.last B.best C.first D.fastest 12A.strong B.nervous C.excited D.careful 13A.anything B.something C.everything D.nothing 14A.turneddown B.turnedoff C.turnedin D.turnedaway 15A.kept B.suggested C.practiced D.considered 16A.taught B.lent C.showed D.saved 17A.detail B.understanding C.method D.goal 18A.cost B.meaning C.happiness D.challenge 19A.hired B.treated C.encouraged D.punished 20A.respect B.praise C.envy D.impress
等比数列{an}中a6＝6a9＝9则a3等于
已知一个圆锥底面半径为1母线长为3则该圆锥内切球的表面积为
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