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人教版高中政治必修1社會主義市場經(jīng)濟教案
教師總結(jié)：社會主義市場經(jīng)濟是使市場在國家宏觀調(diào)控下起基礎(chǔ)性配置作用的經(jīng)濟，充分發(fā)揮市場基礎(chǔ)性調(diào)節(jié)作用，就必須主要靠經(jīng)濟手段、法律手段，而不是行政手段。（三）課堂總結(jié)、點評這節(jié)課我們重點學(xué)習(xí)了社會主義市場經(jīng)濟的有關(guān)知識，知道了社會主義市場經(jīng)濟的基本特征，以及國家宏觀調(diào)控的含義、目標(biāo)和主要手段。這對于我們在經(jīng)濟生活中正確地認(rèn)識我國市場經(jīng)濟的性質(zhì)和作用，理解國家宏觀調(diào)控的措施及意義，增強社會主義優(yōu)越感和民族自強意識，自覺投身現(xiàn)代化建設(shè)等將有重大指導(dǎo)作用?！镎n余作業(yè) 討論：聯(lián)系經(jīng)濟生活中國家宏觀調(diào)控的實例，討論應(yīng)如何認(rèn)識和理解國家各種宏觀調(diào)控手段的綜合運用，對國民經(jīng)濟發(fā)展的意義。★教學(xué)體會 本節(jié)內(nèi)容與學(xué)生生活實際聯(lián)系密切，在學(xué)習(xí)中應(yīng)該多引入日常生產(chǎn)、生活中常見的一些宏觀調(diào)控實例，讓學(xué)生去深刻理解、把握宏觀調(diào)控手段及其作用。
新人教版高中英語必修1Unit 1 Teenage Life-Reading and Thinking教案
【教材分析】The topic of this unit is about teenage life, which belongs to the theme context of “humans and oneself”.As teenagers who shoulder the responsibility of “Chinese great dream”, they must fully know themselves, including their strengths, weaknesses and challenges etc. They are supposed to improve themselves continuously and readily study their subjects, and thus foster their strategies and confidence in lifelong studies.This period is entitled the freshmen challenges, which mainly concerns some big challenges for new students in Senior high school. In this period, a teacher should lead students to find out what their challenges are and guide them to figure out how to crack the challenges and better themselves. More importantly, a teacher should instruct students to absorb new language points and appreciate the language. Besides, a teacher must instruct students to acquire some skills concerning reading efficiently and inspire them to talk more about their new school life, especially their new problems and solutions both at school and in life.【教學(xué)目標(biāo)與核心素養(yǎng)】1. Enable students to acquire the basic usage of the new words and expressions concerning the freshmen challenges and learn to use them flexibly.2. Enable students to have a good understanding of the freshmen challenges in the new senior high school which is quite different from junior middle school.3. Develop students’ sense of cooperative learning and individual thinking capability. 4. Develop students’ different learning skills to solve different reading comprehensive problems.
新人教版高中英語必修1Unit 1 Teenage Life-Reading for Writing教案
【教材分析】This teaching period mainly deals with reading for writing a letter of advice. Students are expected to learn the knowledge about how to write a suggestion letter. The teacher is expected to enable students to master some writing skills concerning suggestion letters and learn to write one.【教學(xué)目標(biāo)與核心素養(yǎng)】1. Get students to have a good understanding of how to write a suggestion letter properly.2. Enable students to use some writing skills flexibly.3. Develop students’ writing and cooperating abilities.4. Strengthen students’ great interest in writing discourses.【教學(xué)重難點】1. How to enable students to have a good understanding of the skills of writing a suggestion letter2.How to enable students to write a good recommendation letter using some writing skills properly.【教學(xué)過程】Step 1: Lead in Begin the class with the lead-in questions: how to write a letter for advice? What kinds of aspects should be included? It is strongly recommended that the teacher should ask students to discuss the topic freely with their partners and brainstorm some ideas concerning the topic. In this way, students can come up with more ideas and avoid being nervous at the beginning of the class.Step 2: Read to discover details concerning advice letters’ writing style.The teacher is expected to ask students to read a letter offering some advice on page 18 silently and then request students to discuss the questions below.
新人教版高中英語必修1Unit 3 Sports and Fitness-Reading and Thinking教案
2. Sort out detailed information about Michael Jordan.（1） Understand the transitional sentence.Q: Which part is about Michael Jordan as a master? Which part is about the example he set?（2） Have the Ss Focus on why Michael Jordan is a master and what good examples Michael Jordan set when they’re reading. And think about these questions as below:Q1: How does the author describe his impressive skills?Q2: How do you understand “time seemed to stand still”?Q3: What does “graceful” mean?Q4. Which sentence do you think best describes his mental strength?Q5. Which words is important in the sentence in describing his mental strength? Why?Q6: How do you understand “unique”?Q7: What can we learn from Michael Jordan?Step 5 Discussing and recommendingRecommend their own living legends of sports.Work in groups to choose your own living legend of sports and give the reasons of your choice. Step 6 HomeworkReview the stories of Lang Ping and Michael Jordan, and try to retell them.
新人教版高中英語必修1Unit 3 Sports and Fitness-Reading for Writing教案
Then have them write a short paragraph to describe and explain their changes. After that, get the Ss to exchange their drafts with their partners and use the checklist to give feedback on their drafts, and finally revise it.Step 5 Summary of how to write a wellness book1.健康書的審題步驟：第一步：明確要求該寫作屬于經(jīng)驗分享，故要用第一人稱來寫;時態(tài)以一股現(xiàn)在時為主。第二步：確定段落該類文章可以從以下三個方面人手:Para.1首先表明寫作的目的Para.2自己的做法及心得體會Para.3表示期望及感謝第三步：提煉要點2.健康書常見句式：1) It is an honor for me to share my favorite sport with you,2) It makes me feel relaxed playing with my friends.3) It makes me rid myself of stress while playing with my friends.4) Moreover, it provides me a valuable chance to communicate with others.5) I we eat too little or too much, or if we choose the wrong food, we may become sick.6) We can do something to change the poor situation.Step 6Homework假如你的老師讓你在班級Wellness Bok上分享自己的親身經(jīng)歷及心得，請根據(jù)以下要點寫一篇80字左右的文章1. 你喜歡的運動是什么？2. 你最喜歡的原因是什么？3. 你參加鍛煉的體會。
新人教版高中英語必修1Unit 4 Natural Disasters- Reading for writing教案
①標(biāo)題——標(biāo)題應(yīng)當(dāng)簡潔明了。②導(dǎo)語——導(dǎo)語是消息開頭的第一段或第一句話，簡明扼要地揭示出消息的核心內(nèi)容。③主體——主體是消息的主要部分，要用充足的事實表現(xiàn)主題，對導(dǎo)語的內(nèi)容作進(jìn)一步的展開和闡述。④結(jié)束語——通常是對全文內(nèi)容進(jìn)行概括性的總結(jié)。3. 新聞報道增分句子（1）陳述事實常用的句型:①A terrible storm hit/struck ... , killing ..②It was a cool autumn night when the earthquake happened. A large number of buildings fell down and roads were destroyed, leaving a great many people homeless.地震發(fā)生在一個涼爽的秋夜。大量的建筑物倒塌，道路被毀,許多人無家可歸。③With the help of the rescue team, people who were the trapped in the flood were saved.在救援隊的幫助下，困在洪水中的人們得救了。（2）陳述觀點常用的句型:①Clearly/Obviously/In my opinion/It seemed that people were shocked.顯然/在我看來/似乎人們震驚了。②The whole city was in ruins after the earthquake.地震后整個城市成了一片廢墟。（3）揭示原因常用的句型:Because of/As a result of/Thanks to the help of the army, people who got injured were sent to the hospital immediately.
新人教版高中英語必修1Unit 4 Natural Disasters-Discovering Useful Structures教案
【教材分析】This teaching period mainly deals with the grammar: the restrictive relative clauses.This period carries considerable significance to the cultivation of students’ writing competence and lays a solid foundation for the basic appreciation of language beauty. The teacher is expected to enable students to master this period thoroughly and consolidate the knowledge by doing some exercise of good quality.【教學(xué)目標(biāo)與核心素養(yǎng)】1. Get students to have a good understanding of the basic usages of the restrictive relative clauses.2. Enable students to use the restrictive relative clauses flexibly.3. Develop students’ speaking and cooperating abilities.4. Strengthen students’ great interest in grammar learning.【教學(xué)重難點】How to enable students to have a good understanding of the restrictive relative clauses, especially the uses of the relative words such as which, that, who, whom.【教學(xué)過程】Step1: 語法知識呈現(xiàn)定語從句（一）—關(guān)系代詞的用法在復(fù)合句中, 修飾名詞或代詞的從句叫定語從句。定語從句通常由關(guān)系代詞或關(guān)系副詞引導(dǎo)，說明事物的具體信息，從句位于被修飾詞之后。被定語從句修飾的詞叫先行詞，引導(dǎo)定語從句的詞叫關(guān)系詞，關(guān)系詞指代先行詞，并在定語從句中充當(dāng)成分。關(guān)系詞有兩種：關(guān)系代詞who, whom ,whose, that, which, as和關(guān)系副詞when, where, why。
新人教版高中英語必修1Unit 4 Natural Disasters-Listening and Speaking教案
【教材分析】高考聽力材料的選用非常重視語言真實性和交際性的原則，語言材料一般來源于實際生活，對話的內(nèi)容大都取材于日常生活，即衣、食、住、行、工作、學(xué)習(xí)、天氣、生活環(huán)境等話題，可分為校園、公共場所、家庭等方面，如: shopping, finding the way, doing one’s homework, seeing a doctor, making a phone call, weather report, asking for different kinds of information等。新教材的特點就是利用生活中真實文本，只是降低難度，讓學(xué)生注重語言的應(yīng)用，將是我們高考把握方向的重要因素?！窘虒W(xué)目標(biāo)與核心素養(yǎng)】學(xué)習(xí)能力目標(biāo)：在聽力當(dāng)中，學(xué)生應(yīng)該有效規(guī)劃學(xué)習(xí)方法，選擇恰當(dāng)?shù)牟呗耘c方法。這節(jié)課的訓(xùn)練目標(biāo)是讓學(xué)生有正確的預(yù)測和抓住問題的關(guān)鍵信息，從而用心去聽來找尋關(guān)鍵信息。根據(jù)生活中實際情況和高考常見語境，我們不難發(fā)現(xiàn)提前預(yù)測和抓住題干中的w很重要，即what, where, when, why等等。
新人教版高中英語必修1Welcome Unit-Discovering Useful Structures教案
II Learn the technical terms-2.1. What can be used as “Subject, Object, Predicative, Direct Object, Indirect Object and objective complement” in a sentence?2. What can be used as “adverbial” in a sentence?3. What can be used as “verb” in a sentence?Answers to questions 1-3:1. Nouns, pronouns and appellations can be used as “Subject, Object, Predicative, Direct Object, Indirect Object and Objective Complement”. Besides, adjectives can be used as “Predicative and Objective Complement” in a sentence.2. Adverbs and prepositional phrases can be used as “Adverbial”.3. Verbs with actual meaning can be used as “Verb” in a sentence. Auxiliary verbs alone cannot be used as “Verb” in a sentence.III Learn to recognize the sentence structures.1. SV structure. For Example:(1) A bird flies.S V(2) A monkey jumps.S V(3) A fish swims.S V√ In SV structures, verbs are “intransitive verbs”.2. SVO structure. For Example:(1) A sheep eats grass.S V O(2) They like bananas.S V O(3) He wants candy.S V O√ In SVO structures, verbs are “transitive verbs”.3. SP structure. For Example:(1) This is great.S P (2) He looks well.S P (3) She became a teacher.S P √ In SP structures, Predicatives are formed by “l(fā)ink verbs” and “adjectives or nouns”.√ link verbs: be, become, grow, look, feel, taste, etc.4. SV IO DO structure. For Example:(1) He asked me a question.S V IO DO(2) Danny wrote me a letter.S V IO DO(3) Billy brought Sam a kite.S V IO DO√ In SV IO DO structures, the verbs are transitive and are followed by two objectives – pronouns or nouns as Indirect Objective, and nouns as Direct Objectives.
新人教版高中英語必修1Welcome Unit-Discovering Useful Structures & Listening and Talking教案
常跟雙賓語的動詞有：（需借助to的）bring, ask, hand, offer, give, lend, send, show, teach, tell, write, pass, pay, promise, return等；基本句型 五S +V + O + OC（主＋謂＋賓＋賓補）特點：動詞雖然是及物動詞，但是只跟一個賓語還不能表達(dá)完整的意思，必須加上一個補充成分來補足賓語，才能使意思完整。 判斷原則：能表達(dá)成—賓語 是…/做…注：此結(jié)構(gòu)由“主語+及物的謂語動詞+賓語+賓語補足語”構(gòu)成。賓語與賓語補足語之間有邏輯上的主謂關(guān)系或主表關(guān)系，若無賓語補足語，則句意不夠完整?？梢杂米鲑e補的有：名詞，形容詞，副詞，介詞短語，動詞不定式，分詞等。如：He considers himself an expert on the subject.他認(rèn)為自己是這門學(xué)科的專家。We must keep our classroom clean.我們必須保持教室清潔。I had my bike stolen.我的自行車被偷了。We invited him to come to our school.我們邀請他來我們學(xué)校。I beg you to keep secret what we talked here.我求你對這里所談的話保密。用it做形式賓語，而將真正的賓語放到賓語補足語的后面，以使句子結(jié)構(gòu)平衡，是英語常用的句型結(jié)構(gòu)方式。即：主語+謂語+it+賓補+真正賓語。如：We think it a good idea to go climb the mountain this Sunday.
新人教版高中英語必修1Unit 5 Languages Around the World-Reading and Thinking教案
【教材分析】本節(jié)課是高中英語第一冊的最后一個單元的閱讀和思考部分，文章難度明顯增加，體現(xiàn)在以下幾個方面：文章題材是說明文，比較難理解；話題生疏，涉及到歷史等知識；生詞量增大，而且在語境中理解詞匯的要求提高。面對這些，教師的難度和高度也要有所提升，通過探討說明順序，了解背景知識等幫助他們找到說明文閱讀的方法?！窘虒W(xué)目標(biāo)與核心素養(yǎng)】1. 文化意識目標(biāo)新課程中指出，文化意識是對中外文化的理解和對優(yōu)秀文化的認(rèn)同。文化意識的的培養(yǎng)有助于學(xué)生增加國家認(rèn)同和家國情懷，成為有文明素養(yǎng)和社會責(zé)任感的人。我們這個單元很好體現(xiàn)了這一點，通過了解漢字書寫的體系和發(fā)展，學(xué)生可以有一種文化自豪感，同時也能夠幫助學(xué)生深入挖掘這篇文章，從而想到更多和中國文化相關(guān)的方面。2. 學(xué)習(xí)能力目標(biāo)
新人教版高中英語必修1Welcome Unit-Reading for Writing教案
教學(xué)目標(biāo)知識目標(biāo)：讓學(xué)生更好理解如何恰當(dāng)?shù)貙懸粋€人的信息介紹，并能讓學(xué)生熟練地使用一些寫作技能。能力目標(biāo)：培養(yǎng)學(xué)生的寫作能力和團隊協(xié)作能力。情感目標(biāo)：提升學(xué)生對寫作的興趣。教學(xué)重難點 教學(xué)重點：如何能讓學(xué)生更好地理解個人信息介紹。教學(xué)難點：如何能讓學(xué)生通過適當(dāng)?shù)厥褂靡恍懽骷寄軄韺懸黄^好的個人信息介紹。教學(xué)準(zhǔn)備 多媒體、黑板、粉筆一、Pre-class1. Greetings2. Leading-inAsk students how to write a profile. What kinds of aspects should be included? The teacher asks students to discuss the topic with each other and put forward to much more ideas about the answer.二、While-class1. The teacher lets students to read the student profiles on Page 8 silently and then asks students to discuss the questions below.1. What is Ann like? How do you know?2. What are Thando’s hobbies?3. Where does Thando come from?4. What is Thando’s dream?5. What does “You will never see me without a book or a pen” mean?
高中物理必修1教案高中物理必修二圓周運動教案
一、描述圓周運動的物理量 探究交流 打籃球的同學(xué)可能玩過轉(zhuǎn)籃球，讓籃球在指尖旋轉(zhuǎn)，展示自己的球技，如圖5-4-1所示.若籃球正繞指尖所在的豎直軸旋轉(zhuǎn)，那么籃球上不同高度的各點的角速度相同嗎?線速度相同嗎? 【提示】 籃球上各點的角速度是相同的.但由于不同高度的各點轉(zhuǎn)動時的圓心、半徑不同，由v=ωr可知不同高度的各點的線速度不同.
人教版高中政治必修2人民民主專政：本質(zhì)是人民當(dāng)家作主教案
4、民主和專政（1）民主，是指在范圍內(nèi)，按照和來共同管理國家事務(wù)的國家制度。民主具有鮮明的，民主總是屬于。世界上從來沒有的民主。（2）專政，即主要依靠實行的統(tǒng)治。（3）民主制國家是民主和專政的辯證統(tǒng)一（對立統(tǒng)一）①民主和專政相互區(qū)別、相互對立，民主只適用于，專政則適用于。②民主與專政是相輔相成、互為前提。民主是專政的，專政是民主的。（4）人民民主專政也是民主與專政的辯證統(tǒng)一。三、必須堅持人民民主專政（1）堅持人民民主專政的必然性（原因）第一、堅持人民民主專政是之一，四項基本原則是我國的，是我國國家生存發(fā)展的。第二、堅持人民民主專政是社會主義現(xiàn)代化建設(shè)的。①只有充分發(fā)揚社會主義民主，確保的地位，保證人民，尊重和保障，才能。②只有堅持國家的專政職能，打擊，才能保障，維護(hù)。（2）堅持人民民主專政的新的要求：
人教版高中政治必修2人民民主專政：本質(zhì)是人民當(dāng)家作主教案
三、堅持人民民主專政教師活動：請同學(xué)們閱讀教材P7頁，思考下列問題：為什么要堅持人民民主專政？現(xiàn)階段如何堅持人民民主專政？學(xué)生活動：閱讀課本，找出問題。1、堅持人民民主專政的重要性（1）堅持人民民主專政是四項基本原則之一，是我國的立國之本。（2）堅持人民民主專政是現(xiàn)代化建設(shè)的政治保證。堅持人民民主，才能調(diào)動人民現(xiàn)代化建設(shè)的積極性；堅持對敵對勢力的專政，才能保障人民民主，維護(hù)國家安定。2、堅持人民民主專政的新的時代內(nèi)容突出經(jīng)濟建設(shè)服務(wù)職能；為改革開放和現(xiàn)代化建設(shè)創(chuàng)造良好國內(nèi)外環(huán)境；重視法制建設(shè)，依法治國；發(fā)展人民民主，加強民主制度建設(shè)。（三）課堂總結(jié)、點評本節(jié)內(nèi)容講述了我國的國家性質(zhì)的有關(guān)知識，懂得我國是人民民主專政的社會主義國家，其本質(zhì)是人民當(dāng)家作主，我國的人民民主具有廣泛性和真實性，是真正的大多數(shù)人的統(tǒng)治，必須堅持人民民主專政。
人教版高中語文必修2《想象世界學(xué)習(xí)虛構(gòu)》教案2篇
虛構(gòu)不等于說假話。它是一種源于生活，但高于生活的藝術(shù)真實。我們可以舉個例子：我國公認(rèn)的最權(quán)威最真實的史書是——《史記》，那么，大家認(rèn)為《史記》里有沒有虛構(gòu)呢？有。必修一的《鴻門宴》里就有虛構(gòu)。大家想：司馬遷是哪個朝代的人？西漢漢武帝時。劉邦項羽是哪個朝代的？秦末時期。那司馬遷不可能坐時光穿梭機到秦末去參加鴻門宴吧？既然他沒不在場，那課文《鴻門宴》里人物的語言、動作、甚至是表情從何而來呢？對，是司馬遷根據(jù)有限的史料加以補充，想象、虛構(gòu)出來的。那么，同學(xué)們在寫作文時，也可以不必拘泥于親身經(jīng)歷的事情，畢竟生活是平淡的，畢竟大家的生活閱歷也有限，有時候，我們發(fā)揮想象、虛構(gòu)一個故事來反映生活的真實，也許更生動、也更典型。所以，近年來高考試卷中都提示考生：作文可以大膽想象，編寫故事。按照編故事的方式不同，我們的虛構(gòu)性作文又可以寫哪些類型呢：小說，散文，童話，寓言，科幻，故事新編……
人教版高中語文必修2《直面挫折學(xué)習(xí)描寫》教案2篇
《貧寒是福天道酬勤石智勇從挫折中奮起》也許是自幼的貧寒生活塑造了石智勇內(nèi)向的性格，即使是胸掛金燦燦的獎牌接受全場觀眾歡呼，他的表情也是略顯羞澀的。小時候吃不飽肚皮的經(jīng)歷讓他至今在“最喜歡的東西”一欄還填寫著“食物”二字，而“窮人的孩子早當(dāng)家”的堅韌，卻又是促成他今日輝煌的動力。中國舉重隊副總教練陳文斌賽后說道：“智勇這幾年練得很苦，今天終于有了這樣的成績，這是天道酬勤的結(jié)果。石智勇的奧運會金牌是中國男舉的一次突破，我們非常激動?！痹谙ＥD神話里，命運女神總是讓英雄歷經(jīng)磨難。石智勇也不例外。四年前的悉尼奧運會前夕，他在一次訓(xùn)練中扭傷腳踝，失去了參賽機會?！爱?dāng)時我傷心極了，不敢看電視直播，我怕參賽的選手成績太低了。高點我還好一點，自欺欺人一下說，哎呀好高，自己去了也拿不了冠軍，要是低了，自己沒去，失去冠軍機會，心里痛啊。后來結(jié)果出來，也不怎么高，心里真難受?！?/p>
人教版新課標(biāo)高中物理必修2動能和動能定理教案2篇
二、課堂教學(xué)（課前由科代表發(fā)回預(yù)習(xí)學(xué)案）1、教師根據(jù)預(yù)習(xí)學(xué)案檢查結(jié)果提出問題（用多媒體展示），引導(dǎo)全班討論（重點討論：①、為什么動能的表達(dá)式一定是 mV2 ？你如何得出這個結(jié)論？②、力在一個過程中對物體所做的功，和物體在這個過程中動能的變化量有什么關(guān)系？你如何得出這個結(jié)論？這個做功的力和F=ma中的力F有什么關(guān)系）。有困難的小組應(yīng)及時問老師。老師在這個過程中巡視指導(dǎo)。2、學(xué)生自主閱讀課文“7 動能和動能定理”中的“動能的表達(dá)式”，然后完成如下練習(xí)（教師在此過程中巡視指導(dǎo)）：2.1嘗試推出動能的表達(dá)式（鼓勵會推導(dǎo)的同學(xué)積極上臺板演，老師引導(dǎo)討論）。2.2寫出動能的小結(jié)（認(rèn)真閱讀教材p66倒數(shù)第二段、第三段，結(jié)合你推導(dǎo)動能表達(dá)式的過程，認(rèn)真思考后四人一組討論：①、動能是矢量還是標(biāo)量？②、動能的單位是什么？③、你認(rèn)為應(yīng)從哪幾方面來理解動能？）
人教版新課標(biāo)高中物理必修2曲線運動教案2篇
1、教師先演示投影：把小鋼珠放在黑墨水瓶蓋里轉(zhuǎn)一下（內(nèi)有一點點墨水），再放在半圓形有機玻璃軌道上運動并飛出，讓鋼珠在白紙上留下痕跡，同樣在3/5半圓周，4/5半圓周上運動飛出，讓學(xué)生猜測飛出方向由什么特點？（有機玻璃板說明：厚約5毫米，略小于小鋼珠直徑，圓弧半徑15厘米，MN邊稍長些，以便過MN做直線，根據(jù)半徑大小確定圓心O位置。）學(xué)生猜想：切線方向師：已知圓弧半徑為15厘米。如何驗證？請用幾何方法作圖驗證。生：標(biāo)出飛出點和圓心，做圓心和飛出點的連線，用量角尺量出該連線和飛出軌跡直線的夾角，是否90度。2、再分組實驗，提醒同桌配合，小心鋼珠滾跑。實驗完畢，要求作圖驗證，并互相討論交流。3、交流和結(jié)論：師：要引導(dǎo)學(xué)生得出正確的科學(xué)結(jié)論：“圓周運動的物體的速度方向為該點的切線方向”，而不能直接得出“曲線運動的的物體速度方向為該點的切線方向”。
人教版新課標(biāo)高中物理必修2機械能守恒定律教案2篇
（二）進(jìn)行新課1、動能與勢能的相互轉(zhuǎn)化演示實驗1：如右圖，用細(xì)線、小球、帶有標(biāo)尺的鐵架臺等做實驗。把一個小球用細(xì)線懸掛起來，把小球拉到一定高度的A點，然后放開，小球在擺動過程中，重力勢能和動能相互轉(zhuǎn)化。我們看到，小球可以擺到跟A點等高的C點，如圖甲。如果用尺子在某一點擋住細(xì)線，小球雖然不能擺到C點，但擺到另一側(cè)時，也能達(dá)到跟A點相同的高度，如圖乙。問題：這個小實驗中，小球的受力情況如何？各個力的做功情況如何？這個小實驗說明了什么？學(xué)生觀察演示實驗，思考問題，選出代表發(fā)表見解。小球在擺動過程中受重力和繩的拉力作用。拉力和速度方向總垂直，對小球不做功；只有重力對小球能做功。實驗證明，小球在擺動過程中重力勢能和動能在不斷轉(zhuǎn)化。在擺動過程中，小球總能回到原來的高度。可見，重力勢能和動能的總和保持不變。即機械能保持不變。