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新高考专用备战2024年高考生物易错题易错点03渗透作用和主动运输的深度解读学生版

新高考专用备战2024年高考生物易错题易错点03渗透作用和主动运输的深度解读学生版

易错点03渗透作用和主动运输的深度解读易错陷阱1:质量浓度就是物质的量浓度【分析】渗透系统的溶液浓度指物质的量浓度而非质量浓度,实质是指渗透压,大小取决于溶液中溶质微粒数目。

错陷阱2:主动运输都是ATP直接供能【分析】第一类:直接消耗ATP的主动运输,通常称为泵(ATP驱动泵),ATP驱动泵既是载体同时也是催化ATP水解的酶。

第二类:间接消耗ATP的主动运输。

小肠上皮细胞逆浓度吸收葡萄糖时,没有直接消耗ATP,而是利用Na+浓度差的能量。

但是Na+浓度差的建立是依靠Na+-K+泵的,而Na+-K+需要消耗ATP。

第三类:光驱动:一种噬盐的厌氧细胞膜上特有的蛋白质(细菌视紫红质),可在光能的激发下,逆浓度将H+运出细胞,造成细胞外积累高能浓度H+,这种H+浓度差可被另一种蛋白利用合成ATP。

易错陷阱3:温度仅影响主动运输速率【分析】温度可以通过影响酶的活性进而影响呼吸作用的能量释放来影响物质运输速率,也可以通过影响生物膜的流动性来影响物质运输。

【易错点提醒一】质量浓度≠物质的量浓度(U形管分析)【例1】U形管中装有两种不同的溶液R和S(R溶液为质量分数为10%的蔗糖溶液,S溶液为质量分数为10%的葡萄糖溶液,两种溶质均不能透过半透膜X),两溶液被一半透膜X隔开,如图所示。

当U形管内达到平衡时,液面与浓度的关系应是()A.右侧较高,且平衡时两溶液浓度相等B.两侧高度相等,浓度相等C.右侧较高,且平衡时右侧浓度较大D.左侧较高,且平衡时左侧浓度较大【变式1-1】图中X、Y分别为不同的溶液(浓度均以质量分数表示),且水和单糖能通过半透膜,而二糖、多糖等不能通过半透膜。

下列相关叙述错误的是()A.若X为蒸馏水,Y为30%葡萄糖溶液,现象是左侧液面先下降后上升,最终左右液面持平B.若X为30%葡萄糖溶液,Y为30%淀粉溶液,现象是左侧液面先上升后下降,最终左右液面持平C.若X为30%蔗糖溶液,Y为30%淀粉溶液,现象是左侧液面先上升后稳定D.若X为蒸馏水,Y为30%淀粉溶液,现象是左侧液面先下降后稳定【变式1-2】如图所示U形管中间被一种水分子和单糖可以通过而二糖不能透过的半透膜隔开,现在两侧分别加入摩尔浓度相等的蔗糖溶液和葡萄糖溶液,一定时间后在左侧加入等量的蔗糖酶(不考虑酶的存在所引起的浓度变化)。

高中生物高考易错点05 遗传的细胞基础-2021年高考生物一轮复习易错题(学生版)

高中生物高考易错点05 遗传的细胞基础-2021年高考生物一轮复习易错题(学生版)

易错点05 遗传的细胞基础易错题【01】对分裂过程中DNA、基因、染色体的变化关系理解不到位易错题【02】对减数分裂过程的理解不到位易错题【03】对减数分裂中基因的位置不清01对分裂过程中DNA、基因、染色体的变化关系理解不到位(2020年浙江省高考生物试卷(7月选考)·21)若某二倍体高等动物(2n=4)的基因型为DdEe,其1个精原细胞(DNA被32P全部标记)在培养液中培养一段时间,分裂过程中形成的其中1个细胞如图所示,图中细胞有2条染色体DNA含有32P。

下列叙述错误的是( )A.形成图中细胞的过程中发生了基因突变B.该精原细胞至多形成4种基因型的4个精细胞C.图中细胞为处于减数第二次分裂后期的次级精母细胞D.该精原细胞形成图中细胞的过程中至少经历了两次胞质分裂1.现有A、B两个精原细胞且均含有4对同源染色体,其中A细胞中仅有一对同源染色体上的DNA分子的两条链被15N标记,B细胞中每对同源染色体中仅有一条染色体上的DNA 分子两条链均被15 N 标记。

将上述细胞均放入含14N的培养基中经过一次完整的减数分裂,下列叙述正确的是A.减数第一次分裂前期,A细胞中含15 N标记的DNA分子有8个B.减数第一次分裂中期,B细胞中含15N标记的DNA分子有4个C.减数第二次分裂后期,A形成的细胞中含15N标记的染色体有2条D.减数第二次分裂后期,B形成的细胞中含15 N标记的染色体为2条2.取某动物(XY型,2n=8)的一个精原细胞,在含3H标记的胸腺嘧啶的培养基中完成一个有丝分裂周期后形成两个相同的精原细胞,将所得子细胞全部转移至普通培养基中完成减数分裂(不考虑染色体片段交换、实验误差和质DNA)。

下列相关叙述错误的是( )A.一个初级精母细胞中含3H的染色体共有8条B.一个次级精母细胞可能有2条含3H的X染色体C.一个精细胞中可能有1条含3H的Y染色体D.该过程形成的DNA含3H的精细胞可能有6个02对减数分裂过程的理解不到位(2019浙江4月选考·24)二倍体动物某个精原细胞形成精细胞过程中,依次形成四个不同时期的细胞,其染色体组数和同源染色体对数如图所示:下列叙述正确的是A.甲形成乙过程中,DNA复制前需合成rRNA和蛋白质B.乙形成丙过程中,同源染色体分离,着丝粒不分裂C.丙细胞中,性染色体只有一条X染色体或Y染色体D.丙形成丁过程中,同源染色体分离导致染色体组数减半1.二倍体动物某精原细胞形成精细胞的过程中,先后出现了甲、乙、丙、丁四种细胞,细胞中的核DNA 和染色体相对含量如下图所示。

青岛版二年级数学上册易错题应用题及答案(学生专用)

青岛版二年级数学上册易错题应用题及答案(学生专用)

青岛版二年级数学上册易错题应用题及答案(学生专用)1、刘东要选一种食物和一种饮料,有几种不同的选法?2、希望小学组织160名学生乘4辆车去春游。

3、在一个正方形的四周边种树,每边种6棵树(其中四个角种一棵),一共要种几棵?4、二(1)班有女生22人,有男生26人,做游戏时平均分成6组,每组有几人?5、2辆货车运12台冰箱,一辆运5台,另一辆运多少台?□○□=□()6、学校报告厅有座位400个,一年级有192人,二年级有201人。

请估算一下,两个年级同时参加讲故事比赛,能不能坐得下?(写出过程)答:7、有22条鱼,可以分给几人?还剩几条鱼?8、城关镇礼堂有3000个座位,城关镇的三所小学各有近900名学生,如果这三所学校的学生同时来参加活动,能坐下吗?9、二年级一班全体同学做游戏,分了4个小组,每个小组有9人,如果每个小组有6人,可以分成几个小组?10、小亚有30支笔.捐掉一些后,还有12支,她捐掉多少支笔?11、杯子里的水重多少克?12、体育室还剩多少个篮球?13、班级准备夏令营,有男生32人,女生16人,一辆巴士最多只能坐6人,如果全部上车需要几辆巴士?14、购物。

面包每个6元饼干每盒8元花生每盘9元糖果每盒7元(1)妈妈买了4盒饼干和1盒糖果,一共花了多少元?(2)妈妈付了100元,应找回多少元?(3)妈妈又用剩下的钱买了几盘花生,最后剩16元,妈妈买了几盘花生?(4)请你再提出一个数学问题并解答。

15、一共有多少只天鹅?16、下面是新城超市部分商品的价格。

名称果冻软面包饼干蛋卷价格5元/500克4元/500克8元/500克9元/500克(1)张奶奶买2千克软面包,需要多少元?(2)小明买1千克果冻和500克蛋卷,一共要花多少元?(3)你还能提出其他什么数学问题?请解17、买水果。

4元/500克 5元/500克 6元/500克 10元/500克(1)4个苹果约重1千克,20个苹果大约重多少千克?一共需要多少钱?(2)买1千克葡萄和5千克桃子,共要付多少钱?18、同学们排队做操,小方前面有5人,后面有3人,他们这一队共有几人?□+□+□=□(人)答:一共有()人19、工人叔叔锯木头,锯成两段要5分钟,锯成4段要几分钟?20、一辆公交车上有乘客32人,到十字口站下去9人。

人教版七年级数学易错题难题精选(学生版)+易错题、重点题锦集、汇总大全

人教版七年级数学易错题难题精选(学生版)+易错题、重点题锦集、汇总大全

人教版七年级数学易错题难题精选(学生版)+易错题、重点题锦集、汇总大全人教版七年级数学易错题、重点题锦集★找规律(一)等差数列△123,456,789,( )A.1122B.101112C.11112D.100112解析:相邻两项的差都是333,未知项应该是789+333=1122。

注意,解答数字推理题时,应着眼于探寻数列中各数字间的内在规律,而不能从数字表面上去找规律,比如本题从123,456,789这一排列,便选择101112,肯定不对。

(二)等比数列△2,1,1/2,()。

A.0B.1/4C.1/8D.-1解析:后面的数字与前面数字之间的比值等于一个常数。

比值为1/2,公式:a n=a1q n-1,a n 代表第n个数,a1代表第1个数,q代表比值,第4项就等于2×(1/2)4-1 =2×(1/8)=1/4 (三)平方数列正序:1,4,9,16,25,36,49,64,81,100,121,144,169,196,225,256,289,324,361,400逆序:100,81,64,49,36……△2,4,16,()解析:前一个数的平方等于第二个数,答案为256。

△1,2,5,26,( )解析:前一个数的平方加1等于第二个数,答案为677。

△0,3,8,15,24,()解析:前一个数加1分别得到1,4,9,16,25,分别为1,2,3,4,5的平方△65,35,17,(),1解析:65=82+1,35=62-1,17=42+1,奇位置数时加1,偶位置数时减1,所以下一个数应该是22-1。

△1,4,16,49,121,()A.256B.225C.196D.169解析:从数字中可以看出12,22,42,72,112,正好是1,2,4,7,11,可以看出后项减前项正好是1,2,3,4,5从中可以看出应为11+5=16,162=256。

△2,3,10,15,26,( )A.29B.32C.35D.37解析:看数列为2=12+1,3=22-1,10=32+1,15=42-1,n2+1和n2+1 △1,2,3,7,46,()解析:自身的平方减去前一项的差等于下一项22-1=3,32-2=7,72-3=46,462-7=2109(四)立方数列正序:1,8,27,64,125,216,343,512,729,1000△-1,0,1,2,9,()解析:后项是相邻前一项的立方加1△0,6,24,60,120,()解析:立方减n, 13-1=0,23-2=6,33-3=24 公式n3-n△2,10,30,68,()解析:立方加n,13+1=2,23+2=10,33+3=30,公式n3+n△0,9,26,65,124,()解析:前五项分别为1,2,3,4,5的立方加1或减1,规律为偶数位置加1,奇数位置减1。

新高考专用备战2024年高考英语易错题精选易错点23语法填空:有提示词之名词数词和代词4大陷阱学生版

新高考专用备战2024年高考英语易错题精选易错点23语法填空:有提示词之名词数词和代词4大陷阱学生版

易错点23有提示词之名词和数词和代词易错陷阱1:名词的数易混易错点。

【分析】1.可数名词变复数变化规则掌握不牢2.名词变复数的不规则变化词掌握不牢3.忽视名词单复数与不可数名词作主语时的主谓一致的问题。

4.名词的构词法掌握不牢。

易错陷阱2:忽视句意和名词的格易混易错点。

【分析】受到母语的干扰,常常忽略句意而用错名词所有格。

易错陷阱3:基数词与序数词易混易错点。

【分析】基数词与序数词的变化规律记忆不牢词形拼写错误,其次还有序数词前的冠词用错如,an eight-year-old boy,以及基数词后面的名词单复数的变化形式。

其次还应当掌握倍数的表达法。

易错陷阱4:代词易混易错点。

【分析】代词在语法填空和写作中的错误以人称代词为主,错因大都因为忽略形容词性物主代词和代词宾格以及反身代词的用法区别而错用,重在梳理上下文的句意和指代对象来判断正确的代词形式。

另外,重点考查词it在用法填空中出错主要有以下几点原因。

1.含有it的固定短语记忆不牢。

2.粗心大意或句子成分不会辨析看不出充当形式主语和形式宾语的it。

3.特殊句式中it的用法。

【易错点提醒一】名词的数易混易错点【例1】(广东省2023-2024学年6校高三联考)This stone tablet is relatively well preserved with clear characters,which is significant for studying cultural and economic(activity)in the southern part of Hebei during the Qing Dynasty.【答案】activities【解析】考查名词复数。

句意:该石碑保存较好,字迹清晰,对研究清代冀南地区的文化经济活动具有重要意义。

activity此处意为“活动”,为可数名词,且前无表示单数含义的词修饰,故填复数式。

故填activities。

易错点01 组成细胞的分子-2021年高考生物一轮复习易错题(学生版)

易错点01  组成细胞的分子-2021年高考生物一轮复习易错题(学生版)

易错点01 组成细胞的分子易错题【01】对单体和多聚体的对应关系及元素组成认识不清易错题【02】对细胞中的主要有机物合成场所和主要功能认识不清易错题【03】对自由水和结合水的变化与代谢活性关系认识不清易错题【04】对生物体内主要有机物的鉴定实验原理和现象有混淆01对单体和多聚体的对应关系及元素组成认识不清(2020年天津高考生物试卷·2)组成下列多聚体的单体的种类最多的是( )A.血红蛋白B.DNAC.淀粉D.纤维素【错因】多糖、蛋白质、核酸,是最主要的几种生物大分子有机物,都是由许多基本组成单位(单体)连接而成,多糖的单体是单糖,蛋白质的单体是氨基酸,核酸的单体是核苷酸。

学生在这里要正确识记各种大分子物质的组成单位。

【问诊】血红蛋白属于蛋白质,构成蛋白质的单体是氨基酸,约有20种;组成DNA的单体是脱氧核苷酸,有4种;组成淀粉和纤维素的单体是葡萄糖,所以单体种类最多的是血红蛋白。

【答案】A【叮嘱】有机化合物糖类由C、H、O 3种元素组成生物体维持生命活动的主要能量来源脂质主要由C、H、O组成(C/H比例高于糖类),有些还含N、P脂肪:细胞代谢所需能量的主要储存形式。

类脂中的磷脂:是构成生物膜的重要物质。

固醇:在细胞的营养、调节、和代谢中具有重要作用。

(如:胆固醇、性激素、维生素D)蛋白质干重中含量最多的化合物由氨基酸脱水缩合而成的高分子化合物,是生命除C、H、O、N外,大多数蛋白质还含有S活动的主要承担者核酸由C、H、O、N、P 5种元素构成核酸是细胞内携带遗传信息的载体,在生物的遗传、变异和蛋白质的生物合成中具有极其重要的作用,是一切生物的遗传物质1.下列关于细胞中生物大分子的叙述,错误..的是( )A.碳链是各种生物大分子的结构基础B.糖类、脂质、蛋白质和核酸等有机物都是生物大分子C.细胞利用种类较少的小分子脱水合成种类繁多的生物大分子D.细胞中生物大分子的合成需要酶来催化2.(2019江苏卷·1)下列关于细胞内蛋白质和核酸的叙述,正确的是A.核酸和蛋白质的组成元素相同B.核酸的合成需要相应蛋白质的参与C.蛋白质的分解都需要核酸的直接参与D.高温会破坏蛋白质和核酸分子中肽键02对细胞中的主要有机物合成场所和主要功能认识不清(2019全国卷II·1)在真核细胞的内质网和细胞核中能够合成的物质分别是A.脂质、RNAB.氨基酸、蛋白质C.RNA、DNAD.DNA、蛋白质【错因】对细胞中不同有机物的合成场所分辨不清,影响判断【问诊】内质网可以合成脂质,细胞核中可以发生转录合成RNA,A正确;蛋白质的合成场所是核糖体,B错误;内质网中不能合成RNA,细胞核中可以合成DNA和RNA,C错误;内质网中不能合成DNA,蛋白质的合成场所是核糖体,D错误。

2021年苏教版三年级数学上册应用题易错题(学生专用)

2021年苏教版三年级数学上册应用题易错题(学生专用)

2021年苏教版三年级数学上册应用题易错题(学生专用)1、3年前父子的年龄和是49岁,今年父亲的年龄是儿子年龄的4倍,父子今年各多少岁?2、一个长方形的长是15厘米,宽是10厘米,把它拉成一个平行四边形后,这个平行四边形的周长是多少厘米?3、一件衣服要订9粒纽扣,7件衣服要几粒纽扣?45粒纽扣可以订几件衣服?4、笑笑在读一个小数时.没有看到小数点,结果读成了三千零二,原来的小数只读一个零,原来的小数是多少?5、明明说:“我的左手边是东方。

”你知道明明面向什么方向吗?6、王大伯紧靠一面墙,用篱笆圈出了一块长是10米,宽是7米的无公害蔬菜地(如图).请问他用了多长的篱笆?7、一个长方形花圃的长是10米,宽8米。

平均每平方米施50克肥料,一共要施多少克肥料?8、某电影院2014年7月26日至8月8日举办电影节,电影节共举办多少天?9、哥弟俩共有邮票70张,如果哥哥给弟弟4张邮票,这时哥哥还比弟弟多2张.哥哥和弟弟原来各有邮票多少张?10、周恩来纪念馆里有一条小路,长540m。

在小路一侧,从起点到终点一共放了10个垃圾桶,平均每两个垃圾桶之间相距多少米?11、小娟向东走5步,然后向西走4步,再向东走3步,再向西走2步,再向东走1步,现在小娟在出发点的什么方向几步的地方?12、商店里一支钢笔5.6元,一支毛笔6.8元,一支中性笔比一支钢笔便宜1.8元.买一支中性笔要付多少元?13、小峰的生日是3月18日,如果他今年的生日是星期六,再过23天就是小丽的生日。

你能算出小丽的生日是几月几日和星期几吗?14、小红写作业用了多长时间?15、一场大雨从9:20开始下,到10:55雨停止.共下了几小时几分?16、养蜂厂去年一共收蜂蜜6450kg.如果5箱蜜蜂一年可以酿蜂蜜375kg,照这样计算,这个养蜂厂去年一共养了多少箱蜜蜂?17、一休去河边打水,他有两个桶,大桶能装9升水,小桶能装4升水,要想恰好从河中打上6升的水带回去,他应该怎么办?18、一列火车从甲城开往乙城,行驶速度为120千米/时,4小时到达,返回时提前了1小时到达,返回时这列火车的速度是多少?19、一圈小朋友玩报数拍手游戏,从1开始报起,凡是报到6的倍数的小朋友,要拍一次手;报到带6的数(比如26,65)的小朋友,要拍两次手;报到既是6的倍数又带6的数的小朋友,要拍3次手。

杠杆易错题专练学生版

杠杆易错题专练学生版

杠杆专练及易错题一.选择题(共26小题)1.下列关于杠杆的说法中,错误的是()A.杠杆可以是直的,也可以是弯的B.动力、阻力使杠杆转动方向相反,但他们的方向不一定C.支点可以在杠杆的端点,也可以在力的作用线之间D.杠杆的长度等于动力臂和阻力臂之和2.关于力臂的下列说法中正确的是()A.从支点到动力作用点的距离叫动力臂B.从动力作用点到阻力作用线的距离叫动力臂C.从支点到阻力作用线的距离叫阻力臂D.从阻力作用点到动力作用点的距离叫阻力臂3.下列常用仪器或工具:①量筒;②剪刀:③烧杯;④试管夹;⑤托盘天平;⑥弹簧测力计,工作过程可抽象成一根杠杆的是()A.①②③B.①③⑤C.②④⑤D.④⑤⑥4.一把刻度准确的杆秤,若水果商贩将标准秤砣换成较轻的秤砣卖给小芳1㎏水果,则水果实际质量()A.大于1㎏B.小于1㎏C.等于1㎏D.可能大于1㎏,也可能小于1㎏5.用一只未调横梁水平的天平去称量物体的质量,当物体放在左盘时,右盘放质量为m1的砝码,横梁正好水平,若物体放在右盘,左盘放上质量为m2的砝码,横梁也正好能水平,如果不考虑游码的移动,设m1>m2,则物体的真实质量M及横梁原来的状态是()A.M=,横梁左高右低B.M=,横梁右高左低C.M=(m1+m2),横梁右高左低D.M=(m1+m2),横梁左高右低6.如图所示,轻质杠杆支点为O,在已调平的杠杆两端分别挂上一些钩码,每一个钩码的质量相等,杠杆恰好在水平位置平衡,如果两边各拿走一个钩码,杠杆将()A.仍保持平衡并静止B.不平衡,向顺时针方向转动C.不平衡,向逆时针方向转动D.仍保持平衡,但要转动7.60kg 的人站在跷跷板某一位置时,跷跷板处于如图所示的平衡状态.由此可估测球的质量约为( )A .20kg B . 30kgC . 60kgD .120kg8.下列哪一组所列的器具都是杠杆( ) A . 剪刀、筷子、打气筒 B .锅铲、钓鱼竿、桌子 C . 钢笔、电灯、直尺D . 撬棒、跷跷板、天平横梁9.如图所示的轻质杠杆OA 上悬挂着一重物G ,O 为支点,在A 端用力使杠杆平衡.下列叙述正确的是( )A . 此杠杆一定是省力杠杆B . 沿竖直向上方向用力最小C . 此杠杆可能是省力杠杆,也可能是费力杠杆D . 沿杆OA 方向用力也可以使杠杆平衡10.如图所示的生活用具中,使用时属于省力杠杆的是( ) A .钢丝钳剪铁钉B .食品夹子夹食品C .钓鱼竿钓鱼D .筷子夹菜11.在你学过的简单机械里既可以省力又可费力的机械是( ) A . 杠杆B . 定滑轮C . 动滑轮D . 滑轮组12.(如图所示的各类杠杆中,属于省距离的是( ) A .起子B .修树枝剪刀 C .筷子 D .钢丝钳13.如图是一个指甲剪的示意图,它是由三个杠杆ABC 、OBD 和OED 组成.用它剪指甲时,属于省力杠杆的是( )A.A BC B.O BD C.O EF D.三个都是14.如图是指甲刀的结构图,关于指甲刀下面说法正确的是()A.指甲刀可以看成是由一个省力杠杆和一个费力杠杆组成B.指甲刀可以看成是由一个省力杠杆和两个费力杠杆组成C.指甲刀使用的越久,用它剪指甲就越省力D.用指甲刀剪指甲时,大段的往下剪比小段的往下剪省力15.如图所示,在“研究杠杆的平衡条件”的实验中,若实验时在杠杆的左端悬挂一个物体,右端用弹簧秤拉着,使杠杆在水平位置保持平衡,今握着弹簧秤缓慢地沿图中虚线的位置1移动到2(杠杆始终在水平位置保持平衡),则弹簧秤的示数()A.不断增大B.先增大,后减小C.不断减小D.先减小,后增大16.如图所示,杠杆水平平衡.当两球同时以相同的速度向O点滚动时.(其中M1>M2)杠杆()A.保持平衡B.左边下偏C.右边下偏D.三种情况都有可能17.古代护城河上安装的吊桥可以看成一个以O为支点的杠杆,如图所示.一个人通过定滑轮用力将吊桥由图示位置缓慢拉至竖直位置,若用L表示绳对桥板的拉力F的力臂,则关于此过程中L的变化以及乘积FL的变化情况,下列说法正确的是()A.L始终在增加,FL始终在增加B.L始终在增加,FL始终在减小C.L先增加后减小,FL始终在减小D.L先减小后增加,FL先减小后增加18.如图所示,在轻质杆OB的中点A处,悬挂有重为G的物体M,在端点B施加方向始终跟杆垂直的拉力F,杆从虚线位置沿逆时针方向匀速转至图示位置的过程中,下列叙述中错误的是()A.拉力F逐渐变大B.拉力F始终小于GC.拉力F跟它力臂的乘积不变D.重物M对杠杆拉力的力臂逐渐变大19.如图所示,杠杆上有两个质量不等的球m1>m2,杠杆在水平位置平衡,杠杆自重不计.如果两球以相同的速度向支点运动,则杠杆()A.仍能平衡B.不能平衡,左侧将下沉C.不能平衡,右侧将下沉D.条件不够,无法判断20.如图所示,一根粗细不均匀的木棒放在地面上,如果用始终垂直于棒,并作用于粗端的力F缓缓把棒抬起,则()A.F将越来越大B.F不变C.F将越来越小D.F先变大,后变小21.如图所示,一根重木棒在水平动力(拉力)F的作用下以O点为轴,由竖直位置逆时针匀速转到水平位置的过程中,若动力臂为l,动力与动力臂的乘积为M,则()A.F增大,l增大,M增大B.F增大,l减小,M减小C.F增大,l减小,M增大D.F减小,l增大,M增大22.如图所示,一杠杆在三个大小相同的力F作用下保持平衡,如果将力F均减小一半,则该杠杆将:()A.向左倾斜B.向右倾斜C.仍旧平衡D.无法确定23.三个和尚挑水吃的故事相信大家耳熟能详,甲图中和尚们商量出新的挑水方案,胖和尚一人挑两小桶,瘦和尚和小和尚两人合抬一大桶,以下说法中不正确的是()A.乙图中水桶B向下沉,为保持水平平衡,胖和尚可以将他的肩往后移动一点距离B.乙图中水桶B向下沉,为保持水平平衡,胖和尚可以将后面水桶B往前移动一点距离C.丙图中小和尚为减轻瘦和尚的负担,可以让瘦和尚往前移动一点距离D.丙图中小和尚为减轻瘦和尚的负担,可以将水桶往前移动一点距离24.用撬棒撬石头时,如果先后用大小相等的力沿着图中所示的方向作用在撬棒的一端A 点上,则()A.F1最容易把石头撬起B.F2最容易把石头撬起C.F3最容易把石头撬起D.F4最容易把石头撬起25.汶川地震中,滚滚的山石挡住了道路.增援人员要用撬棒撬开山石,分别沿如图所示的四个方向用力,其中最省力的是()A.沿F1方向B.沿F2方向C.沿F3方向D.沿F4方向26.如图所示,要将一圆柱体重物推上台阶,最小的作用力应是()A.F1B.F2C.F3D.F4二.填空题(共4小题)27.日本丰田汽车公司,因汽车脚垫和油门踏板问题引发了召回事件,其中油门踏板是一种________类(填“杠杆”或“斜面”)简单机械.使用简单机械的好处是_________(填一个方面).请你再举一例生活中的简单机械_______.28.如右图所示,杠杆OA处于水平平衡状态,O为支点,不计杠杆重,在杆的中点C挂一物体G,G=20N,绳子对A点的拉力为F,绳与水平成30°夹角,若OA长24cm,则F= ________N,F的力臂为________cm;当物体G向________点水平移动时,绳子的拉力变大,若绳子只能承受30N的拉力,则物体G最远距O端_________cm29.在机器中一直是利用连杆、杠杆等来进行传动的.自行车、汽车的制动器(刹车)、机器的阀门等都可以利用它们来传动.如图所示,请你画出刹车系统中的阻力的方向,并画出动力臂和阻力臂.30.如图是一种叫做“真好倒”热水瓶的装置,用它倒水时相当于一个杠杆,请在图中正确画出重力的力臂.。

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1. Johnson had made up his mind to give it up, but on _____ second thought he determined to try _____ third time.A.不填;a B不填;不填 C. a; a D. the; a2. In my opinion, all he ___________ good to his students in his class at present. He is very strict in their study.A. does does doesB. does did doC. does does doD. did do does3. It was almost midnight ______ they at last reached ______ used to be a farmhouse.A. before; thatB. since; whereC. that; whichD. when; what4. When the criminal denied his crime, she _____ to having seen the accident.A. provedB. declaredC. statedD. witnessed5. My job is to help those who are junior ______ me in my class.A. thanB. forC. withD. to6. The new product is said ______ . It is of good quality.A. to test outB. to be tested outC. to have been tested outD. having been tested out7. Parents attach great importance to education, so they tend to ______ some money to guarantee their children will be well educated.A. cut outB. set asideC. leave aloneD. adapt to8. He has his faults, but _____, he is a good help.A. in other wordsB. in allC. all in allD. in the meantime9. Those successful deaf dancers think that dancing is an activity ____ sight matters more than hearing.A. whenB. whoseC. whichD. where10. The conclusion ______ the police came to ____ the boss was as much to blame as anyone else for the great fire didn’t satisfy everyone.A. where; thatB. which; itC. that; whenD. that; that11. Never should we forget the war and sufferings ____ caused to the people.A. itB. whichC. thatD. what12. He always checked and rechecked his game and saw _____ he could improve.A. whereB. whenC. whatD. how13. Nobody would stand out admitting the fact, for some reason, ______ they lost the game.A. thatB. whichC. whatD. why14. ______ with all this hard work made it impossible for Helen to go to the concert.A. Having worn outB. To wear outC. Being worn outD. worn out15. Hearing the noise, the man looked forward _______ what was happening.A. to seeingB. to seeC. to be seenD. to have seen16. In front of ______ remained of my old house, I took some pictures and told my son some funny stories about my childhood.A. whichB. whatC. whatD. where17. When travelling in buses or trains, we are likely to have conversations ____ we give information or opinions about different things.A. whereB. whichC. whatD. when18. Little _____ when I took the trip where it would lead me.A. have I knownB. had I knownC. do I knowD. did I know19. The mistakes made by Chinese students are quite different from ____ were made by the Japanese students in English study.A. thatB. whichC. whatD. those20. The detective was desperately searching for a notebook, in which ____ several sketches of the suspect, as well as his information like home address.A. wroteB. was recordedC. was writtenD. were recorded21. The way people hold to the belief ______ a fun-filled life equals happiness actually reduces wheir chances of ever getting real happiness.A. whenB. thatC. in whichD. which22. _______ I can’t understand is _______ he wants to change his mind.A. That; whatB. That; whyC. What; thatD. What; why23. ______ is known to us all is that the old scientist, for ____ life was hard in the past, still works very hard in his eighties.A. As; whomB. What; whomC. It; whoseD. As; whose24. -It’s difficult for college graduates to find a good job in China.-It depends on whether they have _______ it takes to be successful in today’s world.A. thatB. whichC. whatD. whether25. Sometimes we are asked ______ the likely result of the event will be.A. that what we thinkB. what we thinkC. that we thinkD. what do we think26. Out ______, still discussing the fashion show with great interest.A. walked a crowd of young girlsB. did a crowd of young girls walkC. were walking a crowd of young girlsD. a crowd of young girls were walking27. _______ we must do is _____ the use of energy.A. That; to reduceB. How; to reduceC. What; reduceD. That; reduce28. The speech given by Primer Wen Jiabao showed ____ broad knowledge he has.A. whatB. thatC. howD. which29. Everything in life is a matter of choice. With four roads to choose from and with limited knowledge of ______ they lead, which road will you take?A. whereB. whichC. whatD. when30. He was so angry and spoke so fast that none of us understood _____ he said meant.A. thatB. whatC. that thatD. what what31. _____ the right decision _____ the future is probably the most important thing we will ever do in our lives.A. Making; concernedB. Make; concerningC. To make; concernedD. Making; concerning32. Millions of people still live below the poverty line, _______ only hope of a better life is a rapid rate of economic growth.A. in whichB. of whomC. whoseD. who33. I’m afraid that it is you, ______ Bernard, _____ to blame.A. more than; who isB. rather than; that areC. other than; that isD. less than; which are34. - _____ visited the Shanghai World Expo is sure to tell you the place is worthy _____ twice.-You can say that again.A. Those who have; visitingB. Whoever has; visitingC. Those who have; to be visitedD. Whoever has; to be visited35. She’s ______ is known as a nosy person-she is always dying to know what’s going on in others’ lives.A. whatB. whoC. whichD. that36. ( )is the kindness of the nurse that the patient can never be ( )to her.A. So; too thankfulB. Such; so thankfulC. So; that thankfulD. Such; thankful enough37. Only _____ the opening ceremony of the Poetry Club. The majority of the students were having a class then,A. a few people attendedB. did a few people attendC. attended a few peopleD. a few people were attended38. Finally the parcel arrived by post, in which _____ wrapped dozens of old coins.A. has beenB. wereC. have beenD. was39. I had never had such a good opportunity in my life but somehow away ____.A. it wentB. went itC. did it goD. it goes40. Seldom in my life ______ such a big snowstorm as the one in early 2008.A. I did seeB. I have seenC. did I seeD. have I seen41. To those hardworking students _____ the final success.A. belongs toB. will belong toC. belongD. belongs42. _______, Gao Xiaosong was sentenced to 6-month imprisonment-the most severe puninshment about drunk driving-on June 1.A. A public figure though is heB. Public figure though he isC. Public figure he is thoughD. A public figure though he is43. Only by practising a few hours every day _____ be able to master the language.A. you canB. can youC. you willD. will you44. So ______ in the darkness that he didn’t dare to move an inch.A. he was frightenedB. was he frightenedC. frightened he wasD. frightened was he45. Easy as the cause of the accident was _____, they chose to ignore many details in the investigation.A. to discoverB. discoveringC. to be discoveredD. being discovered46. So difficult ____ it to live in an English-speaking country that I determined to learn English well.A. I have feltB. Have I feltC. I did feelD. did I feel47. At no time, as we know, ______ forget that solving Taiwan Issue is entirely internal Chinese affair.A. we canB. we couldC. can weD. could we48. It was _____ the second-hand bus that the mechanic spent the whole afternoon ____ in the workshop.A. in repairing; lockingB. having repaired; lockedC. repairing; lockedD. to repair; being locked49. It _____ we had stayed together for a couple of weeks ____ I found we had a lot in common.A. was until; whenB. was until; thatC. wasn’t until; whenD. wasn’t until; that50. Was it in front of the market _____ was rebuilt two years ago _____ the road accident happened yesterday?A. where; thatB. that; thatC. that; whichD. which; where51. It’s _____ to see crosstalk actors make ______ of each other.A. such fun; funB. such a fun; a funC. so fun; funD. so funny; a fun52. People regarded the wheel as ( ) invention of importance in ( ) human history.A. an; theB. an;/C. the; theD. the; /53. Has ____ chairman of the board announced that Mr. King has been made _____ manager of our company?A. the; /B. the; theC. /; theD. a; a54. -How do you think I can make up with Jack?-Set aside ______ you disagree and try to find _____ you have in common.A. what; whatB. where; whatC. what; whetherD. where; whether55. Brussels, the capital city of Belgium, is _____ home to the European Union, ______organization of European nations.A. the; anB. /; anC. a; anD. /; the56. While he was investigating ways to improve the telescope, Newton made ____ discovery which completely changed _____ man’s understandin g of color.A. a; /B. a; theC. /; theD. the; a57. As ____ humorous people, _____ British like playing a joke on others.A. the; 不填B. 不填; theC. a; theD. the; the58. Judging from _____ look on his face, he must have _____news of great excitement to tell us.A. the; aB. /; /C. the; theD. the; /59. China, with 56.6 million people living in Internet connected homes, is now _______ second only to the US, _____ leading online rating service reported Monday.A. the; aB. 不填; aC. 不填; theD. a; the60. I remembered Alice, my little niece, often asked questions that children _______ would ask.A. twice so old as sheB. twice as old as her ageC. older twice than her ageD. twice of her age61. Much to his surprise, he invited only twenty friends to the dinner, but _____ came.A. twice as many asB. as many as twiceC. twice as manyD. twice more than62. Advertising is in some way different front other forms of communication ______ the advertisers pay for the message____.A. in that; to be deliveredB. in which; to deliverC. that; being deliveredD. where; delivered63. Our factory has been developing rapidly these days. This year’s production is five times ______ it was ten years ago.A. whatB. thatC. whichD. as64. To many basketball fans, nobody but Kobe Bryant and Lebron James ( ) the best in NBA although Kevin Durant, together with Jeremy Lin and many other players, ( ) also performing very well.A. is; isB. is; areC. are; isD. are; are65. He told us sadly that more than one person _______ in the case.A. involvedB. had involvedC. was involvedD. were involved66. Good amounts of sleep every night _____ also important for your health.A. isB. areC. wasD. were67. Most people don’t think of a stamp as a receipt, but that is _____ it really is-a proof of just how much money you paid in advance for mail delivery.A. whoB. howC. whatD. why68. Sixty miles _____ in a single night, so they were exhausted.A. is coveredB. was coveredC. are coveredD. has covered69. ______ an English-Chinese dictionary.A. The students each haveB. The students each hasC. Each the students hasD. Each of the students have70. My family _____ all fond of singing English songs and we can sing _____ than others.A. is; many moreB. are; many moreC. is; much moreD. are; much more71. -Whom did you _____ the packet at the post office?-Jack. There ______ masses of work for him to do, but he managed to finish the work as required.A. have fetched; wasB. have fetch; wereC. have to fetch; wereD. have fetch; was72. The young elephants each ______ as _____ as 200 kilograms, and that old one is three times as _____.A. weighs; much; heavyB. is weighed; many; muchC. are weighed; many; muchD. weigh; much; heavy73. -All but Johnson ______ present at the meeting.-Perhaps he was ill then.A. wasB. wereC. has beenD. have been74. The girl who graduated from college this summer ______ becoming the head of the small village.A. is aimB. is aiming atC. aim atD. is aimed at75. Nobody but doctors and those ____ by Dr. Zhang _____ to enter the patient’s room.A. invited; is allowedB. are invited; are allowedC. being invited; is allowedD. being invited; are allowed76. _____ of the city ______ two small lakes.A. The east; lieB. The east; liesC. East; lieD. East; lies77. More than one _____ the people heart and soul.A. official has servedB. officials have servedC. official has served forD. officials have served for78. A series of stimulus policies and supportive measures taken by the government ______ to promote change in the economic environment in this area.A. is expectedB. are expectedC. is expectingD. are expecting79. In the city, parts of the sewage pipes were _____ up with rubbish because of the heavy rain.A. chokedB. chokingC. to chokeD. blocked80. After winning the first prize, the boy ______ himself ______ pleasure.A. abandoned; inB. was abandoned; toC. abandoned; toD. abandoned; on。

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