模块一专题二随堂反馈练习
外研版-英语-七上Module1 2单元 随堂练习
Module1 Unit2 随堂练习一、用适当的人称代词填空1. Hi, ______ am Xu Lili.2. This girl is my friend. ______ is 10 years old.3. That boy is from England. ______ name is Jack.4. —Are ______ from Class One, Lucy?—Yes, ______ am.5. This is our teacher, Mr Zhang. ______ is 36 years old.二、单项选择1. My name ____ Jack and I ____ a student.A. is; isB. are; areC. are; amD. is; am2. My friend is in ____. He isn’t in my class.A. class twoB. Class TwoC. two classD. Two Class3. —Are you David Brown?— ____.A. Yes, I amB. Yes, I’mC. Yes, he isD. No, you aren’t4. Britney Spears is a singer. Britney is her ____ name and Spear is her ____ name.A. last: firstB. first; lastC. full; firstD. first; full5. It’s nice ____ you.A. meetB. to meetC. meetsD. met三、完成句子1. 伦敦是英国的首都。
London is______ ______ ______England.2. 莉莉和露西是我们的好朋友。
Lily and Lucy______ ______ good friends.3. 这是王明。
模块二总结与反馈作业
模块二作业:1、在这个模块中,你做了哪些事情?在模块二教学前期分析的学习中我做了以下事情:首先学习的是模块二的必选案例《精心分析,适应变化》,在这个案例的学习中我认真学习了《教育技术参考手册》,从中获益匪浅:了解了教学目标分析的作用、教学目标分类的方式、常用的教学目标分析方法、目标阐明的方法、学习者特征分析的作用、学习者特征分析的主要内容等。
学习了这些知识后,我带着案例阅读的五个思考问题进行了案例的阅读,并作出了自己的分析与理解,同理上传作业,与组里的同学一起讨论交流。
其次,在教学前期案例分析观摩与改进、可选案例分析学习中,认真的进行阅读,按要求去处理解决问题,尽可以的一起和同组同学进生交流和讨论,共同提高。
最后,通过可视化工具的学习,我选择了初二历史下册第12课《香港和澳门的回归》一课,就教学目标进行了分析,运用Freemind 软件画出了思维导图,发了新帖和大家分享交流使用Freemind软件及其他软件各自的优点。
2、学完本模块后,你有哪些收获?在模块二的学习过程中,原来自已教学中存在的许多问题逐渐清晰,许多误区逐渐排除,学到了许多能更好为教学服务的做法。
首先,通过模块二的学习,使原有的教学理论知识得到了充实,教学理论水平得到了一定的提高。
特别是在必选案例的学习中,获得了不少自己平时虽有体会但却没有上升到理论高度的新知识。
比如教学目标分析的作用、学习者特征分析的主要内容等。
其次,在这次学习中还学会了使用一种新的辅助教学的软件Freemind的使用,并且利用这个软件自己独立的完成了作业,这个软件非常好,简单又实用,制作框架结构的内容,比如思维导图、单元总结等,让人一目了然,通俗易懂。
最后,深刻的理解了团队合作的优势。
在课余时间学习时,老师们之间互相帮助、互相学习,还可以在网上向同学老师请教,在帖子里发信息进行交流讨论,不断充实自己,提高自己。
3、学完了本模块内容之后,你对培训过程和培训内容有哪些意见和建议?总的来说,无论是在理论方面,还是在实践技能方面,培训内容都非常好,收获颇丰。
中小学教师教育技能培训模块一模块二、答案
中小学教师教育技术培训模块一、模块二答案模块一:培训前的准备活动 1:认识中小学教师教育技术能力建设培训课程第 1 步:我们将要开始学习的课程活动2:结成学习团队,议论学习策略第 3 步:结成学习小组,认识学习伙伴认识您的学友信息后,您想告诉小组内的学友您的长处或希望获取小组内学员的哪些帮助?很快乐能和你们共同借助这个学习平台,参加技术技术的培训。
我将会珍惜此次培训时机。
经过网络学习平台,踊跃参加教学设计技术的交流。
望大家在学习交流过程中留下你们可贵的经验及建议。
第 4 步:议论培训学习策略实践与作业相信您必定有很多参加培训学习的策略和方法,写出来与您同组的学友议论议论:我们经过参加各种技术培训 , 在学习中不停充分自己,在实践中不停提高自己。
对自己此后的教学设计实践有着很大的帮助。
我们必定要掌握好每一次的培训时机,好好为自己充电。
我们的平时行动模式和时间都有很大随机性 , 这样就很难拟定一个固定的 " 周学习规划 ". 所以 , 在办理学习时间和进度时 , 一定要更为灵活 , 要做到见缝插针 , 要点是要有锲而不舍的精力 , 不可以轻易放弃每天的学习 . 还要保持较高的学习效率,以保障每次学习任务保质保量达成。
活动 3:观摩事例,初步构想选题第 1 步:事例观摩,感悟教育技术魅力以我们自己肩负的学科教学设计为例,我们能够经过互联网找到专家名师的博客、讲座、论文等,比如想认识魏书生对教育的见解,您能够经过网络去搜寻,您甚至能够搜寻到视频:运用各种理论及技术,经过对教与学过程及有关资源的设计、开发、利用、管理和评论,实现教育教学设计优化的理论与实践。
充足利用众多的现代科技成就,作为流传教育信息的媒体,为教育供给丰富的物质基础。
教育技术的魅力在哪里?[ 事例 1] 马老师巧用 DVD(资源链接)视频网络教室中的数学研究(资源链接)视频观摩后与学友议论:看了这两段录像,我想到教育技术的魅力在于创新,一个有经验的优异教师,在上课的过程中,他能够掌握必定的技术。
高一外研 必修2 Module1 随堂测试
必修2 Module1 随堂测试xx六中廖礼容I. Complete the sentences using the words as verbs.Example: Stop mothering me! I’m not a child.1. This apartment _________ six people and a dog.2. She ________ the silk gently.3. It _________ really delicious.4. Can you ________ me those papers?2.Complete the following sentences1. Did you ____〔预定〕a seat on a plane yesterday?2. Please ____ 〔递〕me the book.3. They ____ (取名)their dog Bob.4. She ____〔护理;照顾〕her aged mother every day. II Multiple Choices1 Dark clouds are gathering. It _____ rain.A willB is going toC shouldD is to2 My younger sister _____ be 16 years old next year.A willB is going toC shouldD is to3----Who is going to clean the blackboard?----- ____________.A I’m going toB I will notC I wantD I will4 Hundreds of jobs ______ if the factory closes.A loseB will be lostC are lostD will lost5 I’ve won a holiday for two weeks to Florida. I ______ my mum.A am takingB have takenC takeD will have taken6 Because the shop _____, all the T-shirts are sold at half price.A has closed downB closed downC is closing downD had closed down7 Turn on the television or open a magazine and you ______ advertisements showing happy families.A are often seeingB often seeC will often seeD have often seen8 -----You’ve left the light on .------ Oh , so I have . ______ and turn it off.A I’ll goB I have goneC I goD I’m going to9 At this time tomorrow _______ over the Atlantic.A we are going to flyB we will be flyingC we’ll flyD we’re to fly10 I think it is your brother who _____ for the broken glass.A will be punishedB will punishC punishD punishes11 I _____ go to the bed when the door bell rang.A was going toB was toC was about toD would12 I will wait at the school gate until she _____.A comes backB is comingC will come backD come back13 If he _____ to college, he ____ a lot more.A will go; will learnB will go ; is going to leaveC goes ; is going to learnD goes; will learn14 -----Write to me when you get home.--------________A I mustB I shouldC I willD I can15 As soon as he comes back, I will tell him when ______ and see him.A you will comeB will you comeC you comeD do you come16 Let’s keep to the point or we _____ any decisions.A have never reachedB will never reachC never reachD never reached17---- Can I join your club, Dad?-----You can when you _____ a bit olderA getB will getC are gettingD will have get18 I am rather anxious ______ her , for I haven’t heard from her for a long time.A towardsB overC inD about19 I have _______ for about a month.A caught a coldB had a coldC have a coldD catch a cold20 Make _____ that he is at home before you call on him.A sureB sure ofC ofD out21 We saw him _____ the building and go upstairs.A to enterB enterC enteringD entered22 She is always _____ nut she never seems to lose any weight.A eatingB dietingC drinkingD speaking23 People _____ to visit the park may sign up here.A wishB wishedC are wishingD wishing24 Mr. Smith looks very fit. He takes _____ every day.A many exercisesB much exerciseC little exerciseD few exercises25 We are open during _______ working hours.A ordinaryB generalC normalD usual26 The enemy army ____ the small village in order to take it by surprise.A was headingB was heading forC was heading onD was heading upon27 My mother has always made sure ____ very healthy.A us eatingB us to eatC we eatD our eating28 I am ____ of the class team at school and I am also ____ of the Senior High team.A captain , memberB captain ; a memberC the captain; memberD a captain, member29 I’d like _____ a personal computer.A owningB ownC to ownD owned30 The seriously ___ people in the accident were taken to hospital to be treated.A injuringB injuredC hurtingD hurtKeysI houses fingered tastes handbook hand named nursesII 1-5 BAABA 6-10 CCABA 11-15 CADCA 16-20 BADBA 21-25 BBDBC26-30 BCBCB。
2019年秋季外研版英语八年级上册 Modules 1~2 综合练习 包含答案
外研版英语八年级上册Modules 1~2 综合练习一、用括号内所给单词的适当形式填空。
1.He often advises her (eat) healthy food.2.It is sometimes difficult (understand) American and British people. 3.Many students are afraid (take) an English exam.4.I can't understand the (mean) of all the new words.5.(walk) is good for our health.6.Which one is (low), the white door or the yellow door?7.The cat (it) has a very nice small house.8.There are many old family houses in the city (visit).9.Some (tour) are enjoying the beautiful songs at the moment. 10.This is a comfortable city with some beautiful (beach).二、根据汉语意思完成句子,每空一词。
1.Han Mei lives in Beijing with her family (一直). 2.Everyone (同意) me at the class meeting yesterday. 3.(……很难) finish the work in such a short time. 4.You should (向……问好) your friends.5.If you have any difficulties, please your teacher (向……寻求帮助).6.Is the city (……的首都) America?7.They live in a small village (在沿海).8.Tom is (因……而闻名) his songs.9.Is Shanghai bigger than (其他任何一座城市) in China? 10.The population of China (比……多) that of Australia.三、完形填空。
外研英语高一英语模块一-二检测题及答案
高一年级英语试题笔试部分二、单词拼写(共10小题,每小题1分,满分10分)21、My history teacher is very a . He always makes us laugh inthe lesson.22、Xiao Ming is a very i boy. He knows the answer to any question.23、I like m because I enjoy working out problems about number.24、What's you a towards this question?25、I am (惊异) by what you have told me.26、You should give clear (说明) for all the exercises.27、I was (尴尬) by his comments(评论) about my clothes.28、The more he worked, the more (精力充沛的) he became.29、Doing enough (翻译)exercises can improve your composition.30、He was lying in the sun looking very (放松).三、完成句子(共10小题,每小题2分,满分20分)31、The school year (被分成)two semester.32、 (换句话说), the size of Asia is four timesof Europe.33、They painted the walls (在……开始)the year.34、(结果) my work is improving.35、Mrs Li just smiles, (因此)you don't feelcompletely stupid.36、All the children are (盼望)the SpringFestival.37、I suggest you (做) the experiment in another way.38、It is interesting to look at (……之间的差别)schools in different countries.39、My (最初印象) of Mrs Li was that she was nervousand shy.40、The students (参加)all kinds of activitiesafter class.四、单项选择(共5小题,每小题1分,满分5分)41、I'll never forget Paris for the first time.A. to visitB.visitC. visitingD. visited42、It is reported that the USA usesA. as twiceB. twice muchC. twice much asD. twice as much43、The listeners got at the speech by Mr. smith.A. exciting; excitingB. excited; excitedC. exciting; excitedD. excited; exciting44、I'm sorry I can't go. I a report.A. writeB. am writingC. wroteD. was writing45、---- Whose advice do you think I should take?---- .A You speak. B. That's it. C. It's up to you. D. You do it.五、语言结构(共10小题;每小题分,满分10分)仔细阅读下面的短文,短文中有10个空格或划线句子。
2023-2024外研版八年级下册Module1随堂测试练习
2023-2024学年度初二下随堂练习Module 1A. 单词拼写(本大题有5小题, 每小题1分, 共5分)76. I feel a little ___________(紧张的) when I speak English in class.77. The fish ___________(闻起来) delicious.It must be nice to eat.78. Tom is a student and his ____________(业余爱好) are reading and playing basketball.79. Eating too much ___________(食盐) is bad for our health.80. Sally sent me a ___________(口信) last night .B. 短语填空。
(本大题有5小题, 每小题1分, 共5分)81. Mary will go to the best high school in town and I am _________ _______ (感到自豪的) her.82.Children always have a __________ __________(对甜食的爱好).83. I ________ ________(收到.....的来信) my uncle last week.84. My brother wasn’t _______ _________(上学) yesterday because he was ill.85. The children_________ _________(迫不及待) to celebrate Children's Day.C. 组词成句。
(本大题有5小题, 每小题1分, 共5分)86.really , taste, they, sweet ( . )87.quite, I’m, when , with ,shy I’m, strangers ( . )88.sound,the,interesting , movie, doesn’t( . )89.afraid, am, mistakes, I, of,making(. )90.new, looks, house, and, nice,your( . )必背单词1._____________________ v. 听起来;令人觉得2._____________________ n. 眼镜3._____________________ adj. 秀丽的;标准的4._____________________ adj. 令人愉快的;可爱的5._____________________ n. 牛仔裤(复数)6._____________________ n. (头发)金色的;7._____________________ adj. 酸的;馊的8._____________________ n. 最喜欢的人或事9._____________________ adj.做完的10._____________________ n. 小甜饼;曲奇饼必背短语1.尝一尝;试试看___________________________2.取得好成绩___________________________3.首先;起初____________________________4.害怕某事____________________________ 5.对做某事感到兴奋____________________________Module 1参考答案A.单词拼写(本大题有5小题, 每小题1分, 共5分)76.nervous 77.smells 78. hobbies 79.salt 80.messageB.短语填空。
Module 1-2课堂反馈练习
Module 1-2课堂反馈练习一、首字母填空Everyone needs friends, especially t__________. When you feel l________, it’s nice to have a friend to talk, laugh and do things with.My friends have different hobbies. Lingling is in my class, and she’s my c_________. She likes c__________ stamps. Tony is active and he loves playing beach v_________ at the weekends. Daming is my c________ friend and he is very lazy. His hobby is reading books because he thinks that books are very u__________. Last year, I sent him Harry PotterⅡ as a birthday g_______.It’s important for us to treasure our friendship. We shouldn’t care too much about w__________ our friends are rich or not. No m_________ who they are, friendship can never be changed.二、完成句子1. 我出去的时候,桌子有点脏。
你收拾好了吗?When I went out, the desk was a bit dirty. Have you _______________?2. 她不喜欢接受电台采访,因为她认为这占用他太多的时间了。
Module 1 --2同步检测题 外研版英语八年级下册(含答案)
Module 1 同步检测题(建议用时:15 ~ 20分钟满分:40分)姓名得分_________一、根据句意及汉语或首字母提示完成单词。
(每小题1分,共5分)1.Many students feel n_______ before big exams.2.Lucy works very hard and she always gets full m_______ in exams.3.My mother always tells me not to talk to _________(陌生人).4.My _________(最喜欢的) sports are swimming and jogging.5.The orange tastes too _______(酸的).I don’t like it.二、用所给单词的适当形式填空。
(每小题1分,共5分)1.I’m afraid of _________(fly).2.This bed _________(feel) very soft and comfortable.3.My homework is _________(do) now.4.The boy fell off his bike._________(luck),he didn’t get hurt.5.I was so __________(excite) that I won the first prize in the English Speech Contest.三、单项选择。
(每小题1分,共10分)( )1.You’ll feel _________ when you speak in front of so many people,so you can take a deep breath and everything will be fine soon.A.nervousB.braveC.happyD.active( )2.—Would you like to play basketball with us thisafternoon?—_________,but my mother is ill.A.I don’t careB.It’s very nice of youC.Of course notD.My pleasure( )3.I _________ the shops.May I get you something?A.go toB.went toC.am going toD.have gone to( )4._________ special class we had yesterday! We learned about kung fu.A.HowB.WhatC.How aD.What a( )5.I don’t understand what you said.Would you please give me _________ example?A.anotherB.otherC.othersD.the other( )6.The physics problem is so difficult that _________ students can work it out.A.littleB.fewC.a littleD.a few( )ng Ping is a symbol of courage and success,and we _________ her.e fromB.stand forC.are proud ofD.get ready for( )8.—This T-shirt _________ comfortable.I want to buy one.—So do I.A.soundsB.smellsC.tastesD.feels( )9.—What does your father look like?—_________.A.He’s fine and wellB.He’s really a good fatherC.He’s tall and thinD.He likes readi ng very much( )10.It’s going to rain.My mother asked me _________ an umbrella.A.takeB.takesC.tookD.to take四、句子翻译。
2011年高考物理二轮复习 模块一专题二随堂反馈练习
图2-81.(2010年高考山东卷)如图2-8所示,物体沿斜面由静止滑下,在水平面上滑行一段距离后停止,物体与斜面和水平面间的动摩擦因数相同,斜面与水平面平滑连接.图2-9中v、a、F f和s分别表示物体速度大小、加速度大小、摩擦力大小和路程.图2-9中正确的是()图2-9解析:选C.物体由斜面滑下做匀加速运动,后在平面上做匀减速运动,故B错,C对.由v=at知,A错.在斜面上匀加速运动,s=12at2,s∝t2故D错.2.(2010年北京东城检测)图2-10小球从空中自由下落,与水平地面每一次相碰后反弹到空中某一高度,其速度随时间变化的关系如图2-10所示.若g=10 m/s2,则()A.小球第一次反弹后离开地面的速度的大小为5 m/sB.碰撞前后速度改变量的大小为2 m/sC.小球是从5 m高处自由下落的D.小球反弹起的最大高度为0.45 m解析:选D.由v-t图象可知,小球第一次反弹离开地面时速度大小为3 m/s,A项错误;碰撞前后速度改变量Δv=v′-v=-3 m/s-5 m/s=-8 m/s,B项错误;由小球落地时速度v=5 m/s,得小球下落高=1.25 m,C项错误;由小球反弹速度v′=3 m/s,得反弹高度h=v22g度h′=v′2=0.45 m,D项正确.2g3.图2-11(2010年北京西城检测)如图2-11所示,在光滑水平面上运动的小球,刚好能越过一个倾角为α的固定在水平面上的光滑斜面做自由落体运动,落地时的速度为v ,不考虑空气阻力及小球滚上斜面瞬间的能量损失,下列说法正确的是( )A .小球冲上斜面前在水平面上的速度应大于vB .小球在斜面上运动的时间为v /(g sin α)C .斜面的长度为v 2/(2g sin α)D .小球在斜面上运动的加速度大于g sin α解析:选BC.小球以初速度v 0冲上斜面刚好越过斜面自由落体到地面过程中,由机械能守恒得12m v 20=12m v 2,v 0=v ,A 项错;小球在斜面上做匀减速运动a =g sin α,D 项错;由运动学公式得:v =at ,t =v g sin α,B 项正确;斜面长度L =12at 2=12g sin αv 2g 2 sin 2 α,C 项正确.4.(2010年北京西城抽样)在平直道路上,甲汽车以速度v 匀速行驶,当甲车司机发现前方距离为d 处的乙汽车时,立即以大小为a 1的加速度匀减速行驶,与此同时,乙车司机也发现了甲,立即从静止开始以大小为a 2的加速度沿甲运动的方向匀加速运动.则( )A .甲、乙两车之间的距离一定不断减小B .甲、乙两车之间的距离一定不断增大C .若v >2(a 1+a 2)d ,则两车一定不会相撞D .若v <2(a 1+a 2)d ,则两车一定不会相撞解析:选D.在乙车加速到与甲车速度相同之前,两车间距一直在减小;速度相同之后,两车间距就会变大,故选项A 、B 均不对;以乙车为参考系,甲车对乙车的加速度为(a 1+a 2),初速度为v ,距离为d ,由v 2t -v 20=2as 得若v <2(a 1+a 2)d ,则两车就不会相撞.5.如图2-12所示,物体A 的质量M =1 kg ,静止在光滑水平面上的平板车B 的质量为m =0.5 kg ,长L =1 m .某时刻A 以v 0=4 m/s 向右的初速度滑上木板B 的上表面,在A 滑上B 的同时,给B 施加一个水平向右的拉力.忽略物体A 的大小,已知A 与B 之间的动摩擦因数μ=0.2,取重力加速度g =10 m/s 2.试求:图2-12(1)若F =5 N ,物体A 在小车上运动时相对小车滑行的最大距离;(2)如果要使A 不至于从B 上滑落,拉力F 大小应满足的条件. 解析:(1)物体A 滑上木板B 以后,做匀减速运动,有μMg =Ma A ,得a A =μg =2 m/s 2木板B 做匀加速运动,有F +μMg =ma B ,得:a B =14 m/s 2 两者速度相同时,有v 0-a A t =a B t ,得:t =0.25 s.A 滑行的距离:s A =v 0t -a A t 2/2=15/16 m.B 滑行的距离:s B =a B t 2/2=7/16 m最大距离:Δs =s A -s B =0.5 m.(2)物体A 不滑落的临界条件是A 到达B 的右端时,A 、B 具有共同的速度v 1,则:A v v a 22012-=Bv a 212+L又:v 0-v 1a A =v 1a B可得:a B =6 (m/s 2) F =ma B -μMg =1 N若F <1 N ,则A 滑到B 的右端时,速度仍大于B 的速度,于是将从B 上滑落,所以F 必须大于等于1 N.当F 较大时,在A 到达B 的右端之前,就与B 具有相同的速度,之后,A 必须相对B 静止,才不会从B 的左端滑落.即有:F =(m +M )a ,μMg =Ma ,所以:F =3 N若F 大于3 N ,A 就会相对B 向左滑下.综上所述:力F 应满足的条件是:1 N ≤F ≤3 N.答案:(1)0.5 m (2)1 N ≤F ≤3 N。
外研英语高一英语模块一-二检测题及答案
高一年级英语试题笔试部分二、单词拼写(共10小题,每小题1分,满分10分)21、My history teacher is very a . He always makes us laugh inthe lesson.22、Xiao Ming is a very i boy. He knows the answer to any question。
23、I like m because I enjoy working out problems about number。
24、W hat’s you a towards this question?25、I am (惊异) by what you have told me。
26、You should give clear (说明) for all the exercises。
27、I was (尴尬) by his comments(评论) about my clothes.28、The more he worked, the more (精力充沛的) he became。
29、Doing enough (翻译)exercises can improve your composition.30、He was lying in the sun looking very (放松).三、完成句子(共10小题,每小题2分,满分20分)31、The school year (被分成)two semester。
32、 (换句话说), the size of Asia is four timesof Europe.33、They painted the walls (在……开始)the year.34、(结果) my work is improving.35、Mrs Li just smiles, (因此)you don't feelcompletely stupid。
2020年高考物理二轮复习 模块一专题二课后活页训练
1.图2-13(2020年高考安徽卷)为了节省能量,某商场安装了智能化的电动扶梯.无人乘行时,扶梯运转得很慢;有人站上扶梯时,它会先慢慢加速,再匀速运转.一顾客乘扶梯上楼,恰好经历了这两个过程,如图2-13所示.那么下列说法中正确的是( )A.顾客始终受到三个力的作用B.顾客始终处于超重状态C.顾客对扶梯作用力的方向先指向左下方,再竖直向下D.顾客对扶梯作用力的方向先指向右下方,再竖直向下解析:选C.在慢慢加速的过程中顾客受到的摩擦力水平向左,电梯对其的支持力和摩擦力的合力方向指向右上方,由牛顿第三定律,它的反作用力即人对电梯的作用方向指向左下方;在匀速运动的过程中,顾客与电梯间的摩擦力等于零,顾客对扶梯的作用力仅剩下压力,方向竖直向下.2.图2-14(2020年北京西城抽样)在一竖直砖墙前让一个小石子自由下落,小石子下落的轨迹距离砖墙很近.现用照相机对下落的石子进行拍摄.某次拍摄的照片如图2-14所示,AB为小石子在这次曝光中留下的模糊影迹.已知每层砖(包括砖缝)的平均厚度约为6 cm,A点距石子开始下落点的竖直距离约1.8 m,估算照相机这次拍摄的“曝光时间”最接近( )A.2.0×10-1 sB.2.0×10-2 sC.2.0×10-3 sD.2.0×10-4 s解析:选B.石子落到A点速度v=2gh=6 m/s,A→B速度变化不大,可近似看做匀速运动,故t=ABv=0.02 s.选项B正确.3.(2020年郑州市预测卷)如图2-15所示,一根轻绳跨过光滑定滑轮,两端分别系一个质量为m1、m2的物块.m1放在地面上,m2离地面有一定高度.当m2的质量发生改变时,m1的加速度a的大小也将随之改变.以下的四个图象,最能准确反映a与m2间的关系的是( )图2-15图2-16解析:选D.当m2≤m1时,系统静止,a=0,当m2>m1时,对整体有m2g-m1g=(m1+m2)a即a=g-2m1m1+m2g,可见m2→∞时,a→g,故D正确.4.(2020年高考全国卷Ⅱ)两物体甲和乙在同一直线上运动,它们在0~0.4 s时间内的v t图象如图2-17所示.若仅在两物体之间存在相互作用,则物体甲与乙的质量之比和图中时间t1分别为( )图2-17A.13和0.30 sB.3和0.30 sC.13和0.28 sD.3和0.28 s解析:选B.根据速度图象的特点可知甲做匀加速运动,乙做匀减速运动.根据a =Δv Δt 得3a 甲=a 乙,根据牛顿第二定律有F m 甲=13F m 乙,得m 甲m 乙=3,由a 乙=40.4=10 m/s 2=10.4-t 1,得t 1=0.3 s ,B 正确. 5.a 、b 两车在两条平行的直车道上同方向行驶,它们的v-t 图象如图2-18所示.在t =0时刻,两车间距离为d ;t =5 s 时刻它们第一次相遇.关于两车之间的关系,下列说法正确的是( )图2-18A .t =15 s 的时刻两车第二次相遇B .t =20 s 的时刻两车第二次相遇C .在5~15 s 时间内,先是a 车在前,而后是b 车在前D .在10~15 s 时间内,两车间距离逐渐变大解析:选A.由v-t 象可知:0时刻b 车在前a 车在后,因为t =5 s 时a 、b 第一次相遇,且5 s 至10 s 内a 车速度大于b 车速度,故10 s 时a 车在前b 车在后,两车间距最大.又因v-t 图象与时间轴围成的“面积”表示物体在一段时间内发生的位移,10 s 后b 车速度大于a 车速度,可知15 s 时两车第二次相遇.6.图2-19(2020年青岛二模)DIS是由传感器、数据采集器、计算机组成的信息采集处理系统,某课外实验小组利用DIS系统研究电梯的运动规律,他们在电梯内做实验,在电梯天花板上固定一个力传感器,传感器的测量挂钩向下,在挂钩上悬挂一个质量为1.0 kg的钩码,在电梯由静止开始上升的过程中,计算机屏上显示如图2-19所示的图象,则(g取10 m/s2)( )A.t1到t2时间内,电梯匀速上升B.t2到t3时间内,电梯处于静止状态C.t3到t4时间内,电梯处于超重状态D.t1到t2时间内,电梯的加速度大小为5 m/s2解析:选D.0~t1时间内,F1=mg,电梯静止,t1~t2时间内,F2>mg,电梯加速上升,加速度a=F2-mgm= 5 m/s2,A错误,D正确;t2~t3时间内,F3=mg,电梯匀速上升,B错误;t3~t4时间内,F4<mg,电梯减速上升,处于失重状态,C错误.7.图2-20细绳拴一个质量为m的小球,小球用固定在墙上的水平弹簧支撑,小球与弹簧不粘连.平衡时细绳与竖直方向的夹角为53°,如图2-20所示.以下说法正确的是(已知cos 53°=0.6,sin 53°=0.8)( )A.小球静止时弹簧的弹力大小为35 mgB.小球静止时细绳的拉力大小为35 mgC.细绳烧断瞬间小球的加速度立即为gD.细绳烧断瞬间小球的加速度立即为5 3 g解析:选D.细绳烧断前对小球进行受力分析,小球受到三个力的作用:重力mg,竖直向下;弹簧的弹力F,水平向右;细绳的拉力FT,沿细绳斜向上.由平衡条件得:FT cos 53°=mg,FTsin 53°=F.解得FT =53mg,F=43mg细绳烧断瞬间,细绳的拉力突然为零,而弹簧的弹力不变,此时小球所受的合力与FT 等大反向,所以小球的加速度立即为a=53g.故选D.8.(2020年高考宁夏卷)如图2-21所示,一足够长的木板静止在光滑水平面上,一物块静止在木板上,木板和物块间有摩擦.现用水平力向右拉木板,当物块相对木板滑动了一段距离但仍有相对运动时,撤掉拉力,此后木板和物块相对于水平面的运动情况为( )图2-21A.物块先向左运动,再向右运动B.物块向右运动,速度逐渐增大,直到做匀速运动C.木板向右运动,速度逐渐变小,直到做匀速运动D.木板和物块的速度都逐渐变小,直到为零解析:选BC.撤掉拉力时,物块相对木板仍有向左的相对运动,因此物块受的摩擦力仍向右,物块仍加速;木板水平方向受的力只剩下向左的摩擦力,开始减速,当木板和物块速度相等时,它们的摩擦力消失,以后它们一起匀速.9.(2020年高考江苏物理卷)如图2-22所示,以8 m/s匀速行驶的汽车即将通过路口,绿灯还有2 s将熄灭,此时汽车距离停车线18 m.该车加速时最大加速度大小为 2 m/s2,减速时最大加速度大小为 5 m/s2.此路段允许行驶的最大速度为12.5 m/s,下列说法中正确的有( )图2-22A.如果立即做匀加速运动,在绿灯熄灭前汽车可能通过停车线B.如果立即做匀加速运动,在绿灯熄灭前通过停车线汽车一定超速C.如果立即做匀减速运动,在绿灯熄灭前汽车一定不能通过停车线D.如果距停车线5 m处减速,汽车能停在停车线处解析:选AC.如果立即做匀加速直线运动,t1=2 s内的位移s1=vt1+12a1t21=20 m>18 m,此时汽车的速度为v1=v+a1t1=12 m/s<12.5 m/s,汽车没有超速,A项正确;B项错误.如果立即做匀减速运动,速度减为零需要时间t2=va2=1.6 s,此过程通过的位移为s2=12a2t22=6.4 m,C项正确、D项错误.10.图2-23(2020年高考福建卷)质量为2 kg的物体静止在足够大的水平地面上,物体与地面间的动摩擦因数为0.2,最大静摩擦力与滑动摩擦力大小视为相等.从t=0时刻开始,物体受到方向不变、大小呈周期性变化的水平拉力F的作用,F随时间t 的变化规律如图2-23所示.重力加速度g取10 m/s2,则物体在t=0至t=12 s 这段时间的位移大小为( )A.18 mB.54 mC.72 mD.198 m解析:选B.物体与地面之间的摩擦力Ff=μmg=0.2×2×10 N=4 N,结合F t 图象可知,物体在0~3 s内处于静止状态,在3~6 s内做初速度为0的匀加速直线运动,加速度为a=F-Ffm=8-42m/s2=2 m/s2,在3~6 s内的位移s1=12at2=12×2×32m=9 m;在6~9 s内做匀速直线运动,位移为s2=vt=at2=2×32m=18 m;在9~12 s内做匀加速直线运动,位移为s3=at·t+12at2=18 m+9 m=27 m,故总位移s=s1+s2+s3=54 m,选项B正确.11.(2020年合肥质检)一辆值勤的警车停在直公路边,当警员发现从他旁边以v=10 m/s的速度匀速行驶的货车有违章行为时,决定前去追赶,经t=2 s警车发动起来,以加速度a=2 m/s2做匀加速运动,试问:(1)在警车追上货车之前,两车间的最大距离是多少?(2)若警车能达到的最大速度是vm=12 m/s,达到最大速度后匀速运动.则警车发动起来后至少要多长时间才能追上违章的货车?解析:(1)在警车追上货车之前,两车速度相等时,两车间的距离最大,设警车发动起来经时间t′两车速度相等.两车间的距离最大为s.则t′=va=5 s,s=v(t+t′)-12at′2=45 m.(2)若警车的最大速度是vm =12 m/s,则警车发动起来后加速时间为t1,加速位移为s1t 1=vma=6 ss 1=12a t21=36 m<v(t0+t1)=80 m所以警车还没追上货车,这以后匀速运动追赶,设再经时间t2追上:则s1+vmt2=v(t+t1+t2)2所以警车发动起来后追上货车经历的时间为t=t1+t2=28 s.答案:(1)45 m (2)28 s12.(2020年湖北八校联考)某公共汽车的运行非常有规律,先由静止开始匀加速启动,当速度达到v1=10 m/s时再做匀速运动,进站前开始匀减速制动,在到达车站时刚好停住.公共汽车在每个车站停车时间均为Δt=25 s.然后以同样的方式运行至下一站.已知公共汽车在加速启动和减速制动时加速度大小都为a=1 m/s2,而所有相邻车站间的行程都为s=600 m,有一次当公共汽车刚刚抵达一个车站时,一辆电动车刚经过该车站一段时间t=60 s,已知该电动车速度大小恒定为v2=6 m/s,而且行进路线、方向与公共汽车完全相同,不考虑其他交通状况的影响,试求:(1)公共汽车从车站出发至到达下一站所需的时间t是多少?(2)若从下一站开始计算,公共汽车在刚到达第n站时,电动车也恰好同时到达此车站,n为多少?解析:(1)公共汽车启动时加速所用的时间为t1t 1=v1/a得t1=10 s启动加速时行驶的路程为s1s 1=12a t21得s1=50 m上面所求时间和路程同时也是制动减速所用的时间和路程,所以汽车每次匀速行驶所经过的路程为s2s 2=s-2s1得s2=500 m匀速行驶所花时间为t2t 2=s2/v12所以公共汽车在每两站之间运动所经历的时间为t=2t1+t2=70 s.(2)电动车到达第n站所用的总时间为T T=n(t+Δt)+t所以有v2T=ns代入数据可求得n=12.答案:(1)70 s (2)12。
【最新】外研版八年级英语下册模块1随堂检测题(附答案)
新外研版八年级英语下册模块1随堂检测题(I). 指出下列句中主语的中心词① The teacher with two of his students is going to the cinema.② There is an old man coming here.③ The useful dictionary was given by my teacher last year.④To do to day's homework without the teacher's help is very difficult.(II) 选出句中谓语的中心词① I don't like the picture on th e wall.A. don'tB. likeC. pictureD. wall② The days get longer and longer when summer comes.A. getB. longerC. daysD. summer③ Do you usually go to school by bike?A. DoB. usua llyC.goD. bike④ There will be a meeting at the library this afternoon.A. will beB. meetingC. the libraryD. afternoon⑤ Did the twins have porridge for their breakfast?A.DidB. twinsC. haveD. breakfast⑥ Tom didn't do his homework yesterday.A. TomB. didn'tC. doD. his homework⑦ What I want to tell you is this.A. wantB. to tellC. youD. is⑧ We had better send for a doctor.A. WeB. hadC. sendD. doctor⑨ He is interested in music.A. isB. interestedC. inD. music⑩ Whom did you give my book to?A. giveB.didC. whomD. bookIII. 阅读:A man lives in a very tall building. He has a lot of money and he has a parrot at home. It’s a clever bird.Every morning, after the man gets up, the bird says “hello”. When the man comes back from his work, the bird says, “Is that you? Come here. I can see you.” One evening, when the man is sleeping, a thief comes into his building by climbing up the window. When he finds some money and begins to leave the house by climbing down th rough the window again, he hears a voice in the dark.“Hello! Is that you? Come here. I can see you.” The thief is so frightened that he falls down from the window.( )1. A parrot is kind of ________A.thingB. birdC. manD. machine( )2. When does the parrot say “Hello!” to the man?A. After it gets up.B. After the man gets up.C. After the man goes to bedD. After the man has breakfast.( )3. When does the thief come?A. In the afternoonB. In the morningC. The man isn’t at home.D. The man is asleep.( )4. The parrot is the man’s ________.A. neighbourB. enemyC. petD. servant( )5. What do you think of the thief at last?A. He leaves safely.B. He climbs down the building.C. He climbs down the ladder.D. He died.答案:(I )① teacher ② man ③ dictionary ④ To do(II)① B② A ③ C ④ A ⑤ C ⑥ C ⑦ D ⑧ C⑨ A⑩ A(III) BBDCDUNIT 2(I ) 挑出下列句中的宾语① My brother hasn't done his homework.A B C D② People all over the world speak English.A B C D③ You must pay attention to your pronunciation.A B C D④ How many new words did you learn last class?A B C D⑤ Some of the students want to go swimming, how about you?A B C D⑥ The old man said he was ill.A B C⑦ They made him monitor of the class.A B C D⑧You will find the museum on the left.A B C D⑨ You will find it useful after you leave school.A B C D⑩ They didn't know who"Father Christmas"really is.A B C D(II) 挑出下列句中的表语① The old man was feeling very tired.A B C D② Why is he worried about Jim?A B C D③ The leaves have turned yellow.A B C D④ Soon They all became interested in the subject.A B C D⑤ She was the first to learn about it.A B C D(I II) 阅读:Mr. Smith had two sons .One is seven years old, and the other is five. One morning during the holidays, when he was cleaning the car, his younger son came and asked him for some money for sweets.“Sweets are bad for your teeth,” Mr. Smith said. “Take these two oranges instead ,and give one to your elder(年长的)brother,” One of the oranges is quite a lot bigger than the otherone ,and a s the small boy liked oranges very much, he kept that one for himself, and gave his brother the smaller one.When the other boy saw that his brother had a much larger orange than his own ,he said to him, “It’s selfish(自私的)to take the bigger one for yourself. If father had given me the oranges, I ’d have given you the bigger one.”“I know you would,” answered his brother.” That’s why I took it.”1. “What was Mr Smith doing one morning?.2.What did his younger son ask for?.3.Did the son get what he wanted?.4.Who got the bigger orange?.5.Why did the elder brother say that his brother was selfish?.答案:(I)① D ② D ③D ④ A ⑤ B ⑥ C ⑦ C ⑧ C⑨ A ⑩ D(II)①D ② C ③D ④C ⑤B1. He was cleaning his car.2. He asked for some money for sweets.3. No, he didn’t4. The younger one.5. Because he kept the bigger orange for himself.UNIT 3(I) 挑出下列句中的宾语补足语① She likes the children to read newspapers and books in theA B Creading-room.D② He asked her to take the boy out of school.A B C D③ She found it difficult to do the workA B C D④ They call me Lily sometimes.A B C D⑤ I saw Mr Wang get on the bus.A B C D⑥ Did you see Li M ing playing football on the playground just now?A B C (II) 划出句中的直接宾语和间接宾语(5分,5分钟)① Please tell us a story.② My father bought a new bike for me last week.③ Mr Li is going to teach us history next term.④ Here is a pen.Give it to Tom.⑤ Did he leave any message for me?(III) My Favorite Hobby-我的爱好1.我有许多爱好,其中我最喜欢读书。
高考物理二轮复习 模块一专题一随堂反馈练习
图1-161.如图1-16所示,物体A靠在竖直的墙面上,在竖直向上的力F的作用下,A、B均保持静止,则物体B的受力个数为() A.2 B.3C.4 D.5解析:选C.将B隔离进行受力分析,如图所示,它一定受重力G B、A的压力F N和推力F的作用,如果B只受这三个力的作用,它在水平方向受力肯定不能平衡,故B还应受到A施加的摩擦力作用,方向沿A、B 接触面向下,所以B受到四个力作用.2.(2009年高考山东理综卷)如图1-17所示,图1-17光滑半球形容器固定在水平面上,O 为球心.一质量为m 的小滑块,在水平力F 的作用下静止于P 点.设滑块所受支持力为F N ,OP 与水平方向的夹角为θ.下列关系正确的是( )A .F =mgtan θ B .F =mg tan θ C .F N =mgtan θ D .F N =mg tan θ 解析:选A.滑块受力如图,由平衡条件知: F mg =cot θ⇒F =mg cot θ=mg tan θ,F N =mg sin θ.3.(2010年通州模拟)图1-18在固定于地面的斜面上垂直安放一个挡板,截面为14圆的柱状物体甲放在斜面上,半径与甲相等的光滑圆球乙被夹在甲与挡板之间,没有与斜面接触而处于静止状态,如图1-18所示,现在从球心O 1处对甲施加一平行于斜面向下的力F,使甲沿斜面方向极其缓慢地移动,直至甲与挡板接触为止.设挡板对乙的压力为F1,斜面对甲的支持力为F2,在此过程中()A.F1缓慢增大,F2缓慢增大B.F1缓慢增大,F2缓慢减小C.F1缓慢减小,F2缓慢增大D.F1缓慢减小,F2不变解析:选D.将甲、乙两物体看成一个整体,受力分析如图,由平衡条件易得:F2=(m甲+m乙)g cosα,与F的大小无关,所以F2不发生变化;再隔离乙物体,受力分析如图.随着物体甲逐渐靠近挡板,F甲对乙与竖直方向的夹角变小,F1逐渐减小,故D正确.4.图1-19(2010年押题卷)如图1-19所示,用与竖直方向成一定角度的两根轻绳a和b拉一个小球,这时a绳拉力为F a,b绳拉力为F b,两绳相互垂直.现通过定滑轮对绳b向下用力慢慢拉引,直至绳b变化到水平的过程中,绳a和b的拉力变化为()A.绳a的拉力增大B.绳b的拉力增大C.开始时绳a的拉力一定大于绳b的拉力,后来绳a的拉力小于绳b的拉力D.开始时绳a的拉力可能小于绳b的拉力,后来绳a的拉力一定大于绳b的拉力解析:选ABD.小球受三个力作用:重力mg,绳a的拉力F a,绳b的拉力F b,由动态平衡条件知用力慢慢拉引的过程中,F a、F b的合力与小球重力平衡,如图所示,开始时,F a=mg cos θ,F b=mg sin θ.绳b变为水平过程中,θ变大,F a′=mgcos θ,F b′=mg tan θ,故知F a′>F a,F b′>F b,A、B正确;开始时θ大小未知,不能比较F a、F b,后来因F a′为斜边,故F a′>F b′,D正确.5.(2010年高考山东理综卷)图1-20如图1-20所示,质量分别为m1、m2两个物体通过轻弹簧相连接,在力F的作用下一起沿水平方向做匀速直线运动(m1在地面上,m2在空中),力F与水平方向成θ角.则m1所受支持力F N和摩擦力F f正确的是()A.F N=m1g+m2g-F sin θB.F N=m1g+m2g-F cos θC.F f=F cos θD.F f=F sin θ解析:选AC.法一:整体法以m1、m2整体为研究对象受力分析如图所示.则有:f=F cos θN+F sin θ-(m1+m2)g=0所以N=(m1+m2)g-F sin θ.故选项A、C正确.法二:隔离法以m2为研究对象,受力分析如图示.设弹簧弹力F1与竖直方向夹角为α则:m2g+F1cos α=F sin θ①F1sin α=F cosθ②以m1为研究对象,受力分析如图.则:f=F1sin α③N+F1cos α=m1 g ④由①②③④知f=F cos θN=(m1+m2)g-F sinθ.故选项A、C正确.。
2023-2024外研版八年级下册Module2随堂测试练习
2023-2024学年度初二下随堂练习Module 2A. 单词拼写(本大题有5小题, 每小题1分, 共5分)76. My _____________ (梦想) was to be a doctor when I was a child.77. I ___________(邀请) some of my friends to have dinner together last night.78. The house is so expensive that I can’t ____________(买得起) it.79. The company is going to hold a singing ____________(比赛) next month.80. They have been to many countries, but they have never been to ___________(法国).B. 短语填空。
(本大题有5小题, 每小题1分, 共5分)81.Tom __________ __________(编造) an interesting story and told it to his friends.82. The _________ _________ (一等奖) is a movie ticket.83. ________ _________(到目前为止), the number of people using 5G mobile phones has increased largely.84.On New Year’s Eve, we usually __________ _________(倒数) t o welcome the New Year.85. Life in the future will be _________ ____________(与…不同) life today.C. 组词成句&中译英。
Module1Unit2period2(练习及解析)_外研社(三起)四年级英语上册
Module 1 Unit2 period2 (练习及分析) _外研社(三起)四年级英语上册一般说来,“教师”看法之形成经历了十分漫长的历史。
杨士勋(唐初学者,四门博士)《春秋谷梁传疏》曰:“师者教人以不及,故谓师为师资也”。
这儿的“师资”,其实就是先秦此后历代对教师的别称之一。
《韩非子》也有云:“今有不才之子师长教之弗为变”其“师长”自然也见教师。
这儿的“师资”和“师长”可称为“教师”看法的雏形,但仍说不上是货真价实的“教师”,因为“教师”必定要有明确的教授知识的对象和自己明确的职责。
Module1 Unit2-Period2要练说,得练听。
听是说的前提,听得正确,才有条件正确模拟,才能不断地掌握高一级水平的语言。
我在授课中,注意听闻结合,训练少儿听的能力,课堂上,我特别重视教师的语言,我对少儿说话,注意声音清楚,高低起伏,抑扬有致,富饶吸引力,这样能引起少儿的注意。
当我发现有的少儿不专心听别人发言时,就随时夸耀那些静听的少儿,或是让他重复别人说过的内容,抓住教育机会,要求他们专心听,专心记。
平时我还经过各种兴趣活动,培养少儿边听边记,边听边想,边听边说的能力,如听词对词,听词句说意思,听句子辩正误,听故事表达故事,听谜语猜谜底,听智力故事,动脑筋,出想法,听儿歌上句,接儿歌下句等,这样少儿学得生动爽朗,轻松快乐,既训练了听的能力,增强了记忆,又发展了思想,为说打下了基础。
外研社三起点( 2019 秋)第1页/共5页记几千个汉字 ,熟记几百篇文章 ,写出的诗文也是字斟句酌,琅琅上口 ,成为博览群书的文人。
为什么在现代化授课的今天,我们念了十几年书的高中毕业生甚至大学生 ,竟提起作文就头疼 ,写不出像样的文章呢 ? 吕叔湘先生早在 1978 年就尖锐地提出“:中小学语文授课收效差 ,中学语文毕业生语文水平低 ,十几年上课总时数是 9160 课时 ,语文是 2749 课时 ,恰好是 30%,十年的时间 ,二千七百多课时 ,用来学本国语文 , 倒是大多数但是关 ,难道咄咄怪事 ! ”追根问底 ,其主要原因就是腹中无物。
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图2-8
1.(2010年高考山东卷)如图2-8所示,物体沿斜面由静止滑下,在水平面上滑行一段距离后停止,物体与斜面和水平面间的动摩擦因数相同,斜面与水平面平滑连接.图2-9中v 、a 、F f 和s 分别表示物体速度大小、加速度大小、摩擦力大小和路程.图2-9中正确的是( )
图2-9
解析:选 C.物体由斜面滑下做匀加速运动,后在平面上做匀减速运动,故B 错,C 对.由v =at 知,A 错.在斜面上匀加速运动,s =12
at 2,s ∝t 2故D 错.
2.(2010年北京东城检测)
图2-10
小球从空中自由下落,与水平地面每一次相碰后反弹到空中某一高度,其速度随时间变化的关系如图2-10所示.若g =10 m/s 2,则
( )
A .小球第一次反弹后离开地面的速度的大小为5 m/s
B .碰撞前后速度改变量的大小为2 m/s
C .小球是从5 m 高处自由下落的
D .小球反弹起的最大高度为0.45 m
解析:选D.由v -t 图象可知,小球第一次反弹离开地面时速度大小为3 m/s ,A 项错误;碰撞前后速度改变量Δv =v ′-v =-3 m/s -5 m/s =-8 m/s ,B 项错误;由小球落地时速度v =5 m/s ,得小球
下落高度h =v 2
2g
=1.25 m ,C 项错误;由小球反弹速度v ′=3 m/s ,得反弹高度h ′=v ′2
2g
=0.45 m ,D 项正确. 3.
图2-11
(2010年北京西城检测)如图2-11所示,在光滑水平面上运动的小球,刚好能越过一个倾角为α的固定在水平面上的光滑斜面做自由
落体运动,落地时的速度为v ,不考虑空气阻力及小球滚上斜面瞬间的能量损失,下列说法正确的是( )
A .小球冲上斜面前在水平面上的速度应大于v
B .小球在斜面上运动的时间为v /(g sin α)
C .斜面的长度为v 2/(2g sin α)
D .小球在斜面上运动的加速度大于g sin α
解析:选BC.小球以初速度v 0冲上斜面刚好越过斜面自由落体到
地面过程中,由机械能守恒得12m v 20=12
m v 2,v 0=v ,A 项错;小球在斜面上做匀减速运动a =g sin α,D 项错;由运动学公式得:v =at ,t
=v g sin α,B 项正确;斜面长度L =12at 2=12g sin αv 2
g 2 sin 2 α
,C 项正确. 4.(2010年北京西城抽样)在平直道路上,甲汽车以速度v 匀速行驶,当甲车司机发现前方距离为d 处的乙汽车时,立即以大小为a 1的加速度匀减速行驶,与此同时,乙车司机也发现了甲,立即从静止开始以大小为a 2的加速度沿甲运动的方向匀加速运动.则( )
A .甲、乙两车之间的距离一定不断减小
B .甲、乙两车之间的距离一定不断增大
C .若v >2(a 1+a 2)d ,则两车一定不会相撞
D .若v <2(a 1+a 2)d ,则两车一定不会相撞
解析:选 D.在乙车加速到与甲车速度相同之前,两车间距一直在减小;速度相同之后,两车间距就会变大,故选项A 、B 均不对;以乙车为参考系,甲车对乙车的加速度为(a 1+a 2),初速度为v ,距离为d ,由v 2t -v 20=2as 得若v <2(a 1+a 2)d ,则两车就不会相撞.
5.如图2-12所示,物体A 的质量M =1 kg ,静止在光滑水平面上的平板车B 的质量为m =0.5 kg ,长L =1 m .某时刻A 以v 0=4 m/s
向右的初速度滑上木板B 的上表面,在A 滑上B 的同时,给B 施加一个水平向右的拉力.忽略物体A 的大小,已知A 与B 之间的动摩擦因数μ=0.2,取重力加速度g =10 m/s 2.试求:
图2-12
(1)若F =5 N ,物体A 在小车上运动时相对小车滑行的最大距离;
(2)如果要使A 不至于从B 上滑落,拉力F 大小应满足的条件. 解析:(1)物体A 滑上木板B 以后,做匀减速运动,
有μMg =Ma A ,得a A =μg =2 m/s 2
木板B 做匀加速运动,有F +μMg =ma B ,得:a B =14 m/s 2 两者速度相同时,有v 0-a A t =a B t ,得:t =0.25 s.
A 滑行的距离:s A =v 0t -a A t 2/2=15/16 m.
B 滑行的距离:s B =a B t 2/2=7/16 m
最大距离:Δs =s A -s B =0.5 m.
(2)物体A 不滑落的临界条件是A 到达B 的右端时,A 、B 具有共
同的速度v 1,则:A v v a 22012 =B
v a 212+L 又:v 0-v 1a A =v 1a B
可得:a B =6 (m/s 2) F =ma B -μMg =1 N
若F <1 N ,则A 滑到B 的右端时,速度仍大于B 的速度,于是将从B 上滑落,所以F 必须大于等于1 N.
当F 较大时,在A 到达B 的右端之前,就与B 具有相同的速度,之后,A 必须相对B 静止,才不会从B 的左端滑落.
即有:F=(m+M)a,μMg=Ma,所以:F=3 N 若F大于3 N,A就会相对B向左滑下.
综上所述:力F应满足的条件是:1 N≤F≤3 N. 答案:(1)0.5 m(2)1 N≤F≤3 N。