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计算:(﹣1)2+(π﹣3.14)0﹣|﹣2|
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已知u1=20sin314t+π/6Au2=10sin314t-π/3A则
u1比u2超前300
u1比u2滞后300
u1比u2超前900
无法判断
交流电u1=311sin314t-40°v与u2=311sin314t+30°v的关系为
u1滞后u2
u1超前u2
u1、u2同相
从一瓶浓度为20%的消毒液中倒出后加满清水再倒出又加满清水此时消毒液的浓度为
7.2%
3.2%
5.0%
4.8%
已知则sinαcosα=
或
计算题已知某正弦电流i1=15sin314t-π/6i2=20sin314t+π/2试求它们的相位差
如图在平面直角坐标系xOy中已知AD平分∠OABDB⊥ABBC∥OA点D.的坐标为D.0点B.的横坐
(0,2)
(0,
+
)
(0,
)
(0,5)
计算﹣20+﹣1+4cos30°﹣|﹣|
设则
a=1,b=0
a=0,b=-2
a=0,b=1
a=1,b=-2
把a=1b=代入3a-2b2正确的结果是
(31
-2
)
2
(3
-21
)
2
(3×
-2×
)
2
(3×1
-2×
)
2
非预应力钢筋混凝土屋架如下图所示已知集中荷载P=GK+QK静载GK=10.5kN包括构件自重活载QK
8
8
8
10
4
12
4
14
一定温度下浓度均为1mol/L的A2和B2两种气体在密闭容器内反应生成气体C.达平衡后测得cA2=0
2A
2
+B
2
2A
2
B
A
2
+B
2
2AB
A
2
+B
2
A
2
B
2
A
2
+2B
2
2AB
2
有一组正弦交流电压其瞬时值表达式如下u1=Umsin314t+60Vu2=Umcos314t+150
u1和u2
u3和u4
u1和u4
u1、u2和u3
已知函数fx=sinω>0在02]上恰有一个最大值1和一个最小值-1则ω的取值范围为______.
已知交流电压的有效值是220V频率50Hz当t=0时瞬时值为110√2V 则电压的瞬时值表达式为V
u=220sin(314t+30º)
u=220sin(314t-30º)
u=220√2sin(314t+30º)
u=220√2sin(314t-30º)
计算-3=.
i1=8+4sin314ti2=5+4sin314t+60求i=i1-i2的有效值
计算||+π﹣30+﹣1﹣2cos45°.
已知直线⊥平面直线平面给出下列命题①∥⊥②⊥∥③∥⊥④⊥∥.其中正确命题的序号是.
①③
②③④
①②③
②④
1若Φ求的范围2若求的范围.
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下列做法不利于保护环境的是
下列做法可行的是
1目前人类以化石燃料为主要能源.天然气已成为江都市民的主要燃料其主要成分是天然气属于填“可再生能源”或“不可再生能源”写出其主要成分在空气中完全燃烧的化学方程式. 2关注环境已成为一种生活的态度“低能耗”“低废水”“低废弃物”是低碳理念的重要内涵.下列做法符合低碳理念的是. A.发展太阳能风能等新能源B.用淘米水浇花 C.家用电器长期处于待机状态D.推广无纸化办公双面打印文稿
25分假如你是李华.为了提高汉字书写水平你校上周举办了汉字听写大赛和书法大赛.请你给你的美国笔友Peter写一封信介绍该活动. 提示词:汉字听写大赛Chinesecharactersdictationcompetition 书法大赛handwritingcompetition 注意:1词数100~120左右;2可以适当增加细节以使行文连贯;
下列物质由原子构成的是
8分AtschoolIwasinthetopsetformaths.MyteachersrecommendedthatIstudyeconomicsandstatisticsasmyA﹣levelsubjectsbutIhadmymindsetonalifefulfilledbythearts. InfactIwasavictimofagenderstereotypemadestrongersincebirththatmendoscienceandmathsandwomendoartsorlanguages.Computersciencetechnologyandphysicsjustdidnotfigureinmyteenageworldview.Nobodypopularinmyschoolchosetostudythosesubjects. RealitystruckhardwhenIbeganattendingjobinterviewsandinterviewerswouldsay:It'sgreatthatyouspeakforeignlanguagesbutwhatelsedoyoudoNobodyaskedmyfriendswhohadstudiedscienceortechnologythosequestions. Asurveyrecentlyshowedthatthreeofthebest﹣paidjobsforwomenarcinthetechnologysector.It'sasectorthatreallycanchangetheworld.Wemustshowgirlsthattechnologyhasaneffectoneveryindustryouttherefromfashiontoarchitecturetojournalism.Anybodycanlearntocodeandthesedaysit'sasimportantasreadingandwriting.I'verealizedthatatuniversityI'dachievedthewrongkindofliteracy.Notbeingabletocodelimityourimpactontheworldfarmorethananignoranceofgreatliterature. NowIhaveafive﹣year﹣olddaughter.Idon'twanthertoblindlyfollowgenderrolesthewayIdid.Iwanthertoknowthefactthatascienceortechnicaldegreewillnotlimithercreativitybutexpanditandbroadenherhorizonsfarmorethanmyartsbackgroundcould.I'mexposinghertoMinecraftandappswhichhelpimproveanalyticalthinkingandproblemsolvingskills.I'mhopingthatmydaughterwilldiscoverandacceptherpotentialsinscienceandwanttochangetheworld. 1WhatdoestheunderlinedphrasegenderstereotypeinParagraph2referto A.Personallearningstyle. B.Sexcharacteristic. C.Conventionalsexconcept. D.Professiondifference. 2Accordingtotheauthorwhichmaybethebenefitoflearningscience A.Increasingjobpossibility. B.Winningpopularity. C.Improvinglanguagecompetence. D.Enrichingimagination. 3Howdidtheauthorfeelforhermajorchoice A.Satisfied. B.Active. C.Discouraged. D.Regretful. 4Whatmaybethebesttitleforthetext A.ArtorScienceEitherisOK B.GoodSubjectsGoodFuture C.GirlsChooseMoreWisely D.CatchChancesChangetheWorld
化学用语是学习化学的重要工具. 1用化学符号表示 ①两个硝酸根离子②五个氨分子 ③三个铝原子④两个亚铁离子 2请从①活性炭②聚乙烯③熟石灰④氧气中选择适当物质用其序号填空 ①可用于改良酸性土壤的是②可用于急救病人的是 ③能吸附水中色素和异味的是④可做食品包装袋的是. 3写出下列反应的化学方程式 ①稀盐酸除铁锈②实验室用过氧化氢制氧气 ③镁条在氧气中燃烧④曾青得铁化为铜.
下列物质中能用作钾肥的是
利用白云石制备碱式碳酸镁[4MgCO3•MgOH2•4H2O]的流程如图1. 1白云石主要含有MgCO3CaCO3将白云石矿石粉碎后与煤粉混合在混烧立窑中充分煅烧生成MgOCaO混烧中加入煤的作用是.水化时的主要反应为MgO+H2O=MgOH2填化学方程式. 2碳化过程中溶液的pH不断减小为实现镁元素与钙元素的分离需控制溶液的pH在8.5~9之间使得MgOH2转化为可溶的MgHCO32pH=9的溶液呈现填“酸性”“碱性”或“中性”.实验室用pH试纸测定溶液pH的方法是. 3副产品的主要成分是.气体X是.热解时先产生MgCO3•3H2O而后MgCO3•3H2O再分解生成4MgCO3•MgOH2•4H2O若MgCO3•3H2O分解不完全则产品中镁元素的质量分数.填“偏大”“不变”或“偏小” 4混烧时产生大量CO2除直接供给碳化外还可将CO2转化为多种化工产品. ①工业上利用反应CO2+H2HCOOH生产甲酸.反应中的其他条件相同温度CO2起始压力对催化剂的催化活性影响分别如图2所示则最佳的反应温度为℃最佳的CO2压力为MPa. ②CO2和甲烷反应可制合成气CO和H2的混合物是有效利用CO2的另一种方法.在催化剂800℃条件下CO2和CH4以一定比例反应可以完全转化为合成气其化学方程式为.
物质的用途与性质密切相关下列说法不正确的是
8分BigtobaccoiswhatthebossesofseverallargetechnologyfirmshavestartedcallingFacebook.Beingcomparedtothetobaccogiantsisfarfrompraisebutitisnottheonlywide﹣spreadanalogy比拟.AlowerblowisthesuggestionthatFacebookmaybecomelikeYahootheoncehigh﹣flyinginternetfirmthatfell. Evenayearagotheideawouldhavebeenunthinkable.ButsinceJanuaryFacebookhasbecometrappedinaseriesofmisjudgmentsandmissteps.ItbecameclearthatithaddonetoolittletostopRussianinterference干涉inAmerica'selectionin2016.Ithadtoadmitthatithadsharedthepersonaldataof90millionuserswithoutsidefirmswithoutpermission. ThecomparisontoYahooisimperfect.EvenatitspeakYahoo'sbusinesswasneveraslargeandprofitableasFacebook's.OneofthemainreasonsYahoodeclinedisbecauseitlostouttoapowerfulcompetitorGoogleinonlinesearch;MarissaMayeritsbossfrom2012untilitssaletoVerizonlastyearwasunabletorestoreadvertisers'oremployees'confidenceasusersleft. ButpeoplewhowatchedYahoo'sfallingseesimilarities.Executive主管turnoverwasaleadingindicatorofitsdecline;beforeMs.MayerwashiredYahoowentthroughfourchiefexecutivesinthreeyears.Mr.ZuckerbergwhocontrolsthemajorityofFacebook'svotingsharesisnotleavingbutmanytopexecutivesare.ThisyearseveralhaveannouncedtheirdeparturesincludingFacebook'schiefsecurityofficer. Whenadvertisers'faithinFacebookhasbeenshakenpoliticiansinWashingtonarerunningoutofpatiencewiththecompany.Lawmakers'inspectionofthefirmiscausingittobemorecautiousabouthowitusesdatafortargetingadvertisementsandaboutwhatinformationitmakesavailabletooutsiders. Mr.ZuckerbergandMs.SandbergareunderpressuretoprovetoemployeesandadvertisersthatFacebookisnotonlytrustworthybutworthyoftheirtimeandmoney.Iftheycannotdosoandthecompany'ssharepricecontinuesitsslideitispossiblethatMs.Sandbergwillbereplacedinthenextyear.Mr.ZuckerbergwilldoubtlesshavethoughtsaboutYahoo'ssorrytale. 1ForFacebookbeingcomparedtobigtobaccois. A.positive B.ambitious C.creative D.negative 2AccordingtotheauthorwhatdoesFacebookcurrentlyhaveincommonwiththefailedYahoo A.Lettingoutusers'data. B.Beingdeepinfinancialcrisis. C.Leadersareleavingthecompany. D.Layingoffalargenumberofemployees. 3TheauthortriestosupporthisjudgmentaboutFacebookby. A.questioningitsmanagement B.usingevidencerelatedtoit C.analyzingitsfinancialdata D.listingitsadvantagesanddisadvantages 4Whatisthemainideaofthepassage A.Facebookgetstrappedintrouble. B.Twocompaniesaredeepincrisis. C.HowtosaveFacebook. D.Faithismorevaluablethangold.
10分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.作文中共有10处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. I'mwellfeedathomewithDadasmycook.Dadhasacquiredvariouscookingmethodbytrialanderror.Notonlydoeshiscookingappealtomyappetitebutalsoguaranteethediversityofnutritionforme.Dadincludeslargeamountsoffruitsvegetablesorgrainsinmyregularmealstokeepmydietbalanced.ForeachonemealIeatquitealotbutIdon'tactuallyriskanyhealthyproblem.SowhencomparingmewithmyclassmatesIfeelveryluckytolivewithsuchgooddad.Ialsofeelgratefulformydadjustbecauseofwhichhehasbeendoingformeeversince.
将密封良好的方便面从平原带到高原时包装袋鼓起是因为袋内的气体分子
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30分AsIsatmotionlessonthestepsofthepoolwatchingeveryoneelseswimbackandforthIrealizedthatIhadspentmostofmylifewatchingothersenjoythemselves.ItwasthenthatI1alittlegirlstaringatmewithalookofconfusion.Ismiledatherhopingto2theicebytalkingtoher.Unfortunatelymy3failedandshejustkeptonstaring.My4increasedasalittleboyswamuptomeandsaidIfeelsorryforyou. Afterthe5athoughstruckmeIhadtochange6theworldviewedme.BecauseitwaschildrenwhostaredatmethemostIdecidedtowriteachildren'sbookthattaughtthemabout7inafunway.ThisiswhenKatGirlasuperheroina8whohelpschildrenthatarebeingbulliedcameintomymind. Iquickly9insidemyapartmentandbegancreatingthestory.AsIwroteeachwordIcould10myfutureasaworld﹣renownedauthorandpublicspeaker.Myexcitement11likewildfire.Overthenexttwoyearsthestory12manychangesbeforeitsawtheworldinthespringof2011.Myperseverance13paidoff. OnedayIwasinvitedtospeaktothestudentsataneighboringschool.Iconfidentlywheeledintoaclassroomfilledwithstudentswho14atmejustlikethelittlegirlinthepool.HowdoyoufeelwhenyouseemeIaskedthem.Thekidsbravely15Ifeelsorryforyou. Iopenedmybookandstartedreading.ImmediatelyInoticedthechildren'sstaresturnedto16.HowdoyoufeelwhenyouseemeIaskedagain.Without17theyrepliedYouaresocool!Doesyour18flytooIjustsmiledNonotyetbutmaybesomeday.Iknewinmyheartthatthiswas19.Thepasttwoyearshadproventomethatwith20anythingispossible. 1A.suggested B.watched C.appreciated D.noticed 2A.break B.forget C.remove D.deliver 3A.project B.attempt C.anger D.advice 4A.relief B.curiosity C.awkwardness D.encouragement 5A.competition B.encounter C.argument D.interview 6A.what B.when C.how D.why 7A.disabilities B.potentials C.paintings D.manners 8A.pool B.wheelchair C.car D.spaceship 9A.wheeled B.walked C.rushed D.raced 10A.regard B.realize C.consider D.picture 11A.folded B.spread C.recovered D.declined 12A.turneddown B.wentthrough C.lookedup D.gotaround 13A.generally B.carefully C.eventually D.separately 14A.called B.glimpsed C.laughed D.stared 15A.responded B.greeted C.agreed D.continued 16A.doubts B.jokes C.smiles D.tears 17A.hesitation B.discussion C.intention D.imagination 18A.body B.dream C.book D.chair 19A.funny B.strange C.false D.true 20A.generosity B.determination C.popularity D.harmony
下列物质加入到石灰水中有白色沉淀产生的是
分类是学习化学的方法之一.下列物质分类错误的是
取一定质量的石灰石所含杂质不溶于水不与酸反应高温也不分解高温煅烧一段时间后将所得固体与200g溶质质量分数为14.6%的稀盐酸充分反应过滤得到10g滤渣和一定质量的中性溶液则原石灰石中碳酸钙的质量分数是
下列做法对人体健康没有害的是
制备氟化镁MgF2时有如下反应X+6HF=H2SiF6+2H2O则X的化学式为
甲烷和水反应可以制水煤气其反应的微观示意图如图所示 下列对该反应的叙述正确的是
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如图是ABC三种固体物质的溶解度曲线下列分析不正确的是
下列有关实验现象不正确的是
空气和水是重要的自然资源. 1下列物质不属于空气污染物的是能形成硫酸型酸雨的是. A.CO2B.SO2C.NOXD.CO 2下列能溶于水形成溶液的是溶于水pH>7的是. A.食用油B.面粉C.蔗糖D.纯碱 3如图是实验室电解水实验的装置图a试管中产生的气体为水中加入少量氢氧化钠的目的是. 4生活中常用鉴别硬水和软水. 5水常用于灭火其灭火主要原理是.
2015年世界环境日的主题确定为Think.Eat.Save.﹣﹣思前食后厉行节约.下面做法符合这一主题的是
下列除杂设计括号内为杂质所选用试剂和操作都正确的是
“分子机器”是指在分子尺寸上制造的一类分子器件其长短仅相当于1纳米左右1纳米=10﹣9米它的驱动方式是通过外部刺激如电能光照等使分子结构发生改变从而对外做功.下列关于分子机器的说法中正确的是
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