
The theme of this unit is human and nature, focusing on the theme of wildlife protection. Nature is a complex ecosystem, in which there are delicate balance between animals and plants. Because of the role of the food chain, the extinction of one species will produce influence, causing a series of chain reaction. Large scale extinction of species will have a serious and even irreversible impact on the ecosystem, resulting in immeasurable losses. Therefore, it is of great significance to protect wild species. To protect wild species is to protect human beings themselves. The motto of this unit is "when the buying stops, the killing can too,” which is a public service advertising slogan to protect wildlife. It tells people that every rhinoceros horn, every fur, every bowl of shark fin soup, every Ivory product, and every tiger bone product, etc. consumed by human beings, are innocent wild animals slaughtered behind them. The mission of wild aid is to ban illegal trade in endangered wildlife and mitigate climate change. It aims to educate the public to reduce the consumption demand for endangered wildlife products through public publicity and improve the awareness of environmental protection.1. Improve the awareness of wildlife protection by acquiring the knowledge of wildlife protection.2. Focus on environmental protection and protection of all lives.3. Analysis of the living environment of wild animals with appropriate thinking mode.4. Skillfully use the vocabulary and grammar knowledge of this unit to cultivate self-study ability according to the unit content5. Develop cooperative learning ability through discussion and other ways1. Enable the Ss to talk about the current situation of wild animals.2. Guide the Ss to summarize the main idea of each paragraph as well as the main idea of the text.

Step 5 While reading---Task 3Read the text again and answer the following questions.Q1: How many countries does the UK consist of ?4 Q2: What are the four countries of the United Kingdom?England, Wales, Scotland and Northern Ireland Q3: Which two were the first to be joined together ?England and WalesQ4: What are the two chief advantages of studying the history of a country ?The first one is to help you understand more about the country and its traditions.The second one is to make visiting it more enjoyable.Q5: What’s the author’s attitude towards studying the history ?Supportive/positiveStep 6 Post reading---Retell the textThe United Kingdom, Great Britain, Britain, England—many people are confused by (1)_____ these different names mean. In the 16th century, the nearby country of Wales (2) __________(join) to the Kingdom of England. In the 19 th century, the Kingdom of Ireland was added to create the United Kingdom of Great Britain and Ireland. Finally, the southern part of Ireland (3) ______ (break) away from the UK, which resulted in the full name we have today. However, most people just use the (4)_________(shorten) name: the UK. The four countries (5)__________ belong to the United Kingdom work together in some areas. There were four sets of invaders and the last group were the Normans. They had castles (6)_________(build) all around England and made changes (7)__________ the legal system. Studying the history of the country will make your visit much more (8)_________(enjoy). The capital city London is (9)___ ancient port city that has a history (10)______(date) back to Roman times. 1. what 2.was joined 3.broke 4.shortened 5.that 6. built 7.to 8.enjoyable 9.an 10.dating Step 6 Homework

這個(gè)地區(qū)有著深厚的傳統(tǒng)。既學(xué)既練:為了讓更多的外國(guó)游客了解中國(guó)文化,欣賞中國(guó)美麗的自然風(fēng)光,感受中國(guó)發(fā)生的巨大變化,某外文雜志社將出版一本英語(yǔ)小冊(cè)子來(lái)介紹中國(guó)的旅游景點(diǎn)。該雜志社邀請(qǐng)你為該小冊(cè)子寫一篇英語(yǔ)短文來(lái)介紹杭州,內(nèi)容包括:1.杭州的位置(中國(guó)東南部)、面積(16 000多平方公里)及歷史(2 200多年)等;2.杭州的旅游特色(自然風(fēng)景、傳統(tǒng)文化、特色小吃等);3.希望更多的游客來(lái)杭州參觀。注意:1.詞數(shù)80左右;2.可適當(dāng)增加細(xì)節(jié),以使行文連貫。Located in the southeast of China, Hangzhou is a beautiful city.Dating back more than 2,200 years, Hangzhou covers an area of more than 16,000 square kilometers.In Hangzhou, you can visit the West Lake, whose scenery is fascinating.In addition, you can’t miss its cultural relics and historical sites, from which you will learn more about excellent Chinese traditional culture and traditions.In Hangzhou, the special snacks are famous and visitors from different parts of the world think highly of them.As a tourist attraction, Hangzhou attracts a large number of visitors from home and abroad every year.Once you come to China, Hangzhou is a scenic spot you can’t miss.

choir memberspeople to run food stands people to sell festival ticketspeople to sell music CDspeople to set up equipmentmusical performersStep 2: Listen to the announcement again and answer the questions. ? 1. What kind of songs will Grace Davis sing at the festival?? 2. Who can try out as a performer?? 3. What can those who think they do not have musical talent do?? 4. How can students volunteer to take part?? Talking about preferences:? Would you prefer doing ..?? What would you prefer to do?? Would you rather do .... or ….?? What would you rather do?? I'd prefer .... to ..? I'd rather have ... than .. Step 3: Speaking ProjectWork in groups. Role-play the conversation or make a new one.? Debbie: Where have you been? You missed the announcement about the music festival.? John: I was at the doctor's office. Music festival?? Frank: Yes, it's going to be next month on the school sports field. John, you can play the piano. How about playing it at the festival?? John: Well, I'd rather play the violin. I can play Liang Zhu.? Frank: Wow! Sounds good. What about you, Debbie? ? Debbie: Actually, I don't have much musical ability. I'd prefer just to help out with the crowds.? Frank: You can sell tickets or work at a food stand.? John: So can I assume that the aim of the festival is to raise money?? Debbie: Yes. All of the money will go to charity.

Step1:自主探究。1.(教材P52)Born(bear) in the USA on 2 January 1970, Whitacre began studying music at the University of Nevada in 1988.2.(教材P52) Moved(move) by this music, he said, “It was like seeing color for the first time.”3.(教材P56)I was very afraid and I felt so alone and discouraged(discourage).4.(教材P58)Encouraged(encourage) by this first performance and the positive reaction of the audience, I have continued to play the piano and enjoy it more every day.Step2:語(yǔ)法要點(diǎn)精析。用法1:過(guò)去分詞作表語(yǔ)1).過(guò)去分詞可放在連系動(dòng)詞be, get, feel, remain, seem, look, become等之后作表語(yǔ),表示主語(yǔ)所處的狀態(tài)Tom was astonished to see a snake moving across the floor.湯姆很驚訝地看到一條蛇正爬過(guò)地板。Finally the baby felt tired of playing with those toys.終于嬰兒厭倦了玩那些玩具。注意:1).過(guò)去分詞作表語(yǔ)時(shí)與被動(dòng)語(yǔ)態(tài)的區(qū)別過(guò)去分詞作表語(yǔ)時(shí),強(qiáng)調(diào)主語(yǔ)所處的狀態(tài);而動(dòng)詞的被動(dòng)語(yǔ)態(tài)表示主語(yǔ)是動(dòng)作的承受者,強(qiáng)調(diào)動(dòng)作。The library is now closed.(狀態(tài))圖書館現(xiàn)在關(guān)閉了。The cup was broken by my little sister yesterday.(動(dòng)作)昨天我妹妹把杯子打碎了。2)感覺類及物動(dòng)詞的現(xiàn)在分詞與過(guò)去分詞作表語(yǔ)的區(qū)別過(guò)去分詞作表語(yǔ)多表示人自身的感受或事物自身的狀態(tài),常譯作“感到……的”;現(xiàn)在分詞多表示事物具有的特性,常譯作“令人……的”。

This lesson is about music. Students can classify the types of music through the instruments and its sound and can talk about their preferences about music, even join some activities and play a role in them according to their musical talents. On the basis, they are guided to use the languages to express their preferences and some plosive sounds and their rules.1. Classify the music types through the instruments and its sound.2. Listen and understand what the speakers’ preferences are and the reasons; talk about their own preferences and give their own reasons, using these sentences: “What kind of music do you like? And why? “ “Because it makes/gives me energy/peaceful.../touches my heart...”.3. Learn some plosives and the rules.4. Join some activities and play a role in them according to the talents. 1. Listen and understand what the speakers’ preferences are and the reasons;2. talk about their own preferences and give their own reasons, using these sentences: “What kind of music do you like? And why? “ “Because it makes/gives me energy/peaceful.../touches my heart...”.3. Learn some plosives and incomplete plosives and its rules.Step 1 Lead inPoint at the pictures on P50 and ask Q1: What are the people doing in the pictures below?Q2: What kind of music they are?Then play the MP3s one by oneStep 2 ListeningTask 1: A reporter from the school newspaper is interviewing students about music. Listen to the interviews. Draw lines between the words to make complete sentences. Some words will not be used.

This section focuses on "learning about experiencing music Online". This virtual choir is a new form of music performance. Members from all over the world don't need to love to come to a place. Instead, they use the new technology to model the various parts and wonderful virtual harmony group of music in the family. Students need to understand the main meaning of each paragraph. Finding topic sentences is an important way to understand the general idea of a paragraph. After the topic sentence, it is usually the detail sentence that supports and explains the topic sentence. Some paragraphs have obvious subject sentences, for example, the first sentence of the second paragraph is the subject sentence of the paragraph, and the following sentenceStudents need to pay attention to the topic sentences and key sentences, and then pay attention to how the sentences after the meaning explain, explain and support the topic sentences or key sentences before.1.Guide students to learn about experiencing music online2.Guide students to scan and circle the information in the text.3.Guide students to find the numbers and dates to fill in the timeline.4.Guide students to learn more about music by completing the sentences with the correct forms of the words and phrases. And then make a mind map about the outline of the passage.1. Guide students to pay attention to reading strategies, such as prediction, self-questioning and scanning.2. Help students sort out the main meaning of each paragraph and understand the narrative characteristics of "timeline” in illustrative style.3. Lead students to understand the changes that have been caused by the Internet.

The Internet celebrity Gao Yifeng. Years ago, he owned 5 companies and the staffs over 1,000, but during the economy crisis, he became nothing but debt. He was so worried that his hair became white overnight. There was a time when he wanted to killed himself. But after listening to the song Start Over by Liu Huan, he decided to cheer himself up. He started a steamed bun shop and gradually became a national chain shops. Now he became successful again.Walter Haddon said, “Music is the medicine of a troubled mind.” Music contains such a pleasant and inspiring force. Music gave him courage and bravery. When he listened to the song, it made his spirit fly like a kite in the wind. Music gave him strength and brought him relief. It was the rock I leant on to become strong and to get through those hard times. I hope none of us have to go through the same kind of suffering that he did. At the same time, we all go through various periods when we feel sad or alone. During those times, music can help us in the same way that it helped him. I hope we all will somehow begin to treasure music and make it a part of our life. Thank you for your listening !5.Revise your writing each other.Does he/she explain how music has changed his/her/someone else’s life?Are some of the rhetorical devices included and used properly ?Does he/she talk about how music makes him/her/someone feel?Is the first word in each sentences capitalised?Does he/she use correct punctuation ?

【引入新課】同學(xué)們?cè)诤舆呁嫠5臅r(shí)候不知注意到如圖中所展示的場(chǎng)面沒有?(注意到了)那么同學(xué)們知道圖中A、B、C它們的名稱分別是什么嗎?(不知道)它們的名稱簡(jiǎn)單的講可以統(tǒng)稱為河流地貌。至于它們的具體名稱和形成原理就是我們今天要討論的問題。一、河流地貌【介紹】河流地貌是自然界中最常見的地貌之一。按照成因,可以將河流地貌分為侵蝕地貌和堆積地貌,它們的形成和發(fā)展主要與外力作用有關(guān)?!景鍟?、分類: 侵蝕地貌和堆積地貌【過(guò)渡】我們首先來(lái)看一下河流侵蝕地貌【板書】2、河流侵蝕地貌【介紹】河流在流動(dòng)過(guò)程 中,會(huì)破壞并掀起地表的物質(zhì),形成侵 蝕地貌。河流侵蝕地貌是由溯源侵蝕、下蝕和側(cè)蝕共同作用形成的?!疽龑?dǎo)讀書】請(qǐng)同學(xué)們快速閱讀教材P83倒數(shù) 第二段,添出以下表格。

4.海洋污染(1)閱讀書本P64,由學(xué)生歸納:(2)展示圖片資料:“威望號(hào)油輪泄漏事故”【討論】石油污染將對(duì)該海區(qū)的生態(tài)環(huán)境造成怎樣的影響?【小結(jié)】本節(jié)課我們從四個(gè)方面了解了洋流對(duì)地 理環(huán)境和人類活動(dòng)的影響,重點(diǎn)學(xué)習(xí)洋流對(duì)氣候和對(duì)漁場(chǎng)形成的影響。同學(xué)們聽說(shuō)過(guò)“厄爾尼諾”現(xiàn)象嗎?“厄爾尼諾”現(xiàn)象會(huì)影 響秘魯漁場(chǎng)的漁獲量;也會(huì)對(duì)氣候產(chǎn)生影響,導(dǎo)致全球氣候異常?!禾骄俊吧衿娴亩驙柲嶂Z”現(xiàn)象』學(xué)習(xí)小組交流【小結(jié)】“厄爾尼諾”現(xiàn)象還有許多不解之謎,其中之一是形成原因,尚未能解釋清楚。有人認(rèn)為是南半球東南信風(fēng)減弱造成的,也有人認(rèn)為是大氣環(huán)流減弱造成的結(jié)果;且“厄爾 尼諾”現(xiàn)象發(fā)生有沒有自身的規(guī)律?發(fā)生周期長(zhǎng)短受什么制約?等等,這些謎團(tuán)等待我們?nèi)ヒ灰唤忾_。

三維目標(biāo):知識(shí)和技能 1、了解地球自轉(zhuǎn)和公轉(zhuǎn)的方向及一些基本數(shù)據(jù):周期、速度、公轉(zhuǎn)軌道、黃赤交角。2、理解由于地球自轉(zhuǎn)運(yùn)動(dòng)造成的晝夜交替、地方時(shí)差,掌握時(shí)間的有關(guān)換算,能正確判斷晨昏線。3、理解地球自轉(zhuǎn)和公轉(zhuǎn)的關(guān)系,理解太陽(yáng)直射點(diǎn)的南北移動(dòng)的過(guò)程及其原因,并能演示其運(yùn)動(dòng)規(guī)律。4、理 解晝夜長(zhǎng)短和正午太陽(yáng)高度的季節(jié)變壞緯度變化 。過(guò)程與方法 1、通過(guò)運(yùn)用地球儀演示地球的自傳和公轉(zhuǎn)現(xiàn)象,學(xué)生能夠準(zhǔn)確的畫出夏至日到冬至日太陽(yáng)照射地球的示意圖2、能根據(jù)“二分二至日太陽(yáng)照射地球示意圖”分析全球各 地的晝夜長(zhǎng)短和正午太陽(yáng)高度的變化,分析同緯度地區(qū)不同季節(jié)和不同緯度地區(qū)相同季節(jié)的晝夜長(zhǎng)短和正午太陽(yáng)高度的變化。

【轉(zhuǎn)折過(guò)渡】除了以上所說(shuō)的褶皺山和斷層山之 外,是否還有其他類型的山脈呢?試舉一例說(shuō)明?!緦W(xué)生思考后回答】有,如富士山屬于火山?!窘處熆偨Y(jié)】同學(xué)們回答的很好,還有火山,那么火山是如何形成的呢?這就是我們要研究的下一個(gè)問題?!景鍟?、火山【指導(dǎo)讀書】請(qǐng)同學(xué)們閱讀教材P81思考:①玄武巖高原和火山有什么聯(lián)系與區(qū)別? ②火山由哪幾部分構(gòu)成的?③火山的規(guī)模是否相同?【學(xué)生回答】①聯(lián)系:玄武巖高原和火山都是由于處于地下深處的巖漿,在巨大的壓力作用下,有時(shí)候會(huì)沿著地殼的薄弱地帶噴出地表而形成的。區(qū)別:玄武巖高原是巖漿沿著地殼的線狀裂隙流出,往往比較寬廣。如哥倫比亞高原。火山是巖漿沿著地殼的中央噴出口或管道噴出。如我國(guó)長(zhǎng)白山的主峰。②火山由火山口和火山錐兩部分組成。③火山的規(guī)模大小不一,大火山的相對(duì)高度可達(dá)4 000~5 000米,火山口直徑為數(shù)百米;小火山的相對(duì)高度不及100米。

情感、態(tài)度與價(jià)值觀幫助學(xué)生確立事物普遍聯(lián)系的觀點(diǎn)。幫助學(xué)生樹立正確認(rèn)識(shí)利用自然規(guī)律,實(shí)現(xiàn)人類與環(huán)境的和諧發(fā)展的觀念 。教學(xué) 重點(diǎn)水循環(huán)的形成過(guò)程和地理意義。人類活動(dòng)對(duì)水循環(huán)的影響教學(xué) 難點(diǎn)水循環(huán)的地理意義。教具、資料多媒體課件課 時(shí)安排1課時(shí)教學(xué)過(guò)程:【新課導(dǎo)入】出示計(jì)算機(jī)圖片:地球衛(wèi)星圖片、太陽(yáng)系九大行星圖片。請(qǐng)同學(xué)們看,這是人類的家園——地球,與太陽(yáng)系其它大行星相比,它的最大特點(diǎn)是什么呢?(有豐富的水)是的,我們所居住的這顆行星,表面四分之三為水所覆蓋,是一顆“水的行星”。我們這一章要學(xué)習(xí)的就是地球上的水 。【引導(dǎo)】水有哪些物理化學(xué)性質(zhì)?(固液氣三態(tài)變化、比熱、脹縮、溶劑等)那么,地球上的水都存在哪里呢?(海洋、河 流、湖泊、地下、冰川、沼澤、大氣、生物體等)【總結(jié)】水在地理環(huán)境中以氣態(tài)、固態(tài)和液態(tài)三種形式相互轉(zhuǎn)化,形成各種水體,共同構(gòu)成了一個(gè)連續(xù)但不規(guī)則的圈層。這實(shí)際上就是水圈。

過(guò)渡:在實(shí)際生活中,城市內(nèi)部空間結(jié)構(gòu)并非完全按照這一經(jīng)濟(jì)規(guī)律呈現(xiàn),而是更具復(fù)雜性。這說(shuō)明除了經(jīng)濟(jì)因素外,還有很多其他因素在起作用,請(qǐng)大家結(jié)合你的認(rèn)識(shí)、圖2.9和案例1:紐約市的少數(shù)民族區(qū)談?wù)勀愕目捶?。?)其他因素I收入——形成不同級(jí)別住宅區(qū)的常見原因。有能力支付昂貴租金和選擇最佳居住環(huán)境的人,其居住地往往形成高級(jí)住宅區(qū)。II知名度——城市內(nèi)某些地區(qū)在歷史、文化或經(jīng)濟(jì)方面具有很高的聲譽(yù),這往往會(huì)吸引更多新的住宅或商場(chǎng)建在該處,以提高其知名度。III種族聚居區(qū)的形成——在有些城市的某一區(qū)域內(nèi),如果某個(gè)種族或宗教團(tuán)體占優(yōu)勢(shì),就可能形成種族聚居區(qū)。如紐約市的唐人街、哈林區(qū)、小意大利區(qū)等。IV歷史因素——城市的建筑物和街道設(shè)計(jì)可以維持久遠(yuǎn),早期的土地利用方式對(duì)日后的功能分區(qū)有著深遠(yuǎn)的影響。

1.生產(chǎn)上的聯(lián)系:有投入——產(chǎn)出的關(guān)系工業(yè)生產(chǎn)的過(guò)程復(fù)雜,工序繁多,往往需要經(jīng)過(guò)多家工廠的加工才能完成一種產(chǎn)品的生產(chǎn)過(guò)程。因此,在這些工廠之間就存在著產(chǎn)品與原料的聯(lián)系。一家工廠生產(chǎn)的產(chǎn)品是另一家工廠的原料,這兩家工廠之間就形成了工序上的工業(yè)聯(lián)系。2.非生產(chǎn)上的聯(lián)系:如地理空間上的聯(lián)系布局在同一個(gè)工業(yè)區(qū)內(nèi),共同利用工業(yè)區(qū)的道路、供水、供電、通信等基礎(chǔ)設(shè)施以及其他生產(chǎn)、生活服務(wù)設(shè)施,或者共同利用當(dāng)?shù)亓畠r(jià)的勞動(dòng)力,形成了空間利用上的工業(yè)聯(lián)系。我國(guó)許多地方的經(jīng)濟(jì)技術(shù)開發(fā)區(qū)就是建立在這種工業(yè)聯(lián)系基礎(chǔ)上的。(二)工業(yè)集聚1.形成具有工業(yè)聯(lián)系的一些工廠往往近距離地聚集起來(lái),形成工業(yè)集聚現(xiàn)象。2.工業(yè)集聚可獲得效應(yīng)(1)工業(yè)集聚可以加強(qiáng)企業(yè)間的信息交流和技術(shù)協(xié)作,降低中間產(chǎn)品的運(yùn)輸費(fèi)用和能源消耗,進(jìn)而降低生產(chǎn)成本,提高生產(chǎn)效率和利潤(rùn),取得規(guī)模效益。

一般情況下,凡是支持物對(duì)物體的支持力,都是支持物因發(fā)生形變而對(duì)物體產(chǎn)生彈力。所以支持力的方向總是垂直于支持面而指向被支持的物體。例1:放在水平桌面上的書書由于重力的作用而壓迫桌面,使書和桌面同時(shí)發(fā)生微小形變,要恢復(fù)原狀,對(duì)桌面產(chǎn)生垂直于桌面向下的彈力f1,這就是書對(duì)桌面的壓力;桌面由于發(fā)生微小的形變,對(duì)書產(chǎn)生垂直于書面向上的彈力f2,這就是桌面對(duì)書的支持力。學(xué)生分析:靜止地放在傾斜木板上的書,書對(duì)木板的壓力和木板對(duì)書的支持力。并畫出力的示意圖。結(jié)論:壓力、支持力都是彈力。壓力的方向總是垂直于支持面而指向被壓的物體,支持力的方向總是垂直于支持面而指向被支持的物體。引導(dǎo)學(xué)生分析靜止時(shí),懸繩對(duì)重物的拉力及方向。引導(dǎo)得出:懸掛物由于重力的作用而拉緊懸繩,使重物、懸繩同時(shí)發(fā)生微小的形變。重物由于發(fā)生微小的形變,對(duì)懸繩產(chǎn)生豎直向下的彈力f1,這是物對(duì)繩的拉力;懸繩由于發(fā)生微小形變,對(duì)物產(chǎn)生豎直向上的彈力f2,這就是繩對(duì)物體的拉力。

l.知識(shí)與技能:(1)知道摩擦力產(chǎn)生的條件。(2)能在簡(jiǎn)單問題中,根據(jù)物體的運(yùn)動(dòng)狀態(tài),判斷靜摩擦力的有無(wú)、大小和方向;知道存在著最大靜摩擦力。(3)掌握動(dòng)磨擦因數(shù),會(huì)在具體問題中計(jì)算滑動(dòng)磨擦力,掌握判定摩擦力方向的方法。(4)知道影響到摩擦因數(shù)的因素。2.過(guò)程與方法:通過(guò)觀察演示實(shí)驗(yàn),概括出摩擦力產(chǎn)生的條件及摩擦力的特點(diǎn),培養(yǎng)學(xué)生的觀察、概括能力。通過(guò)靜摩擦力與滑動(dòng)摩擦力的區(qū)別對(duì)比,培養(yǎng)學(xué)生分析綜合能力。3.情感態(tài)度價(jià)值觀:在分析物體所受摩擦力時(shí),突出主要矛盾,忽略次要因素及無(wú)關(guān)因素,總結(jié)出摩擦力產(chǎn)生的條件和規(guī)律。二、重點(diǎn)、難點(diǎn)分析1.本節(jié)課的內(nèi)容分滑動(dòng)摩擦力和靜摩擦力兩部分。重點(diǎn)是摩擦力產(chǎn)生的條件、特性和規(guī)律,通過(guò)演示實(shí)驗(yàn)得出關(guān)系f=μN(yùn)。2.難點(diǎn)是學(xué)生有初中的知識(shí),往往誤認(rèn)為壓力N的大小總是跟滑動(dòng)物體所受的重力相等,因此必須指出只有當(dāng)兩物體的接觸面垂直,物體在水平拉力作用下,沿水平面滑動(dòng)時(shí),壓力N的大小才跟物體所受的重力相等。

1.用CAI課件模擬汽車的啟動(dòng)過(guò)程。師生共同討論:①如果作用在物體上的力為恒力,且物體以勻速運(yùn)動(dòng),則力對(duì)物體做功的功率保持不變。此情況下,任意一段時(shí)間內(nèi)的平均功率與任一瞬時(shí)的瞬時(shí)功率都是相同的。②很多動(dòng)力機(jī)器通常有一個(gè)額定功率,且通常使其在額定功率狀態(tài)工作(如汽車),根據(jù)P=FV可知:當(dāng)路面阻力較小時(shí),牽引力也小,速度大,即汽車可以跑得快些;當(dāng)路面阻力較大,或爬坡時(shí),需要比較大的牽引力,速度必須小。這就是爬坡時(shí)汽車換低速擋的道理。③如果動(dòng)力機(jī)器在實(shí)際功率小于額定功率的條件下工作,例如汽車剛剛起動(dòng)后的一段時(shí)間內(nèi),速度逐漸增大過(guò)程中,牽引力仍可增大,即F和v可以同時(shí)增大,但是這一情況應(yīng)以二者乘積等于額定功率為限度,即當(dāng)實(shí)際功率大于額定功率以后,這種情況不可能實(shí)現(xiàn)。

(五)平拋運(yùn)動(dòng)規(guī)律的應(yīng)用例1:一架老式飛機(jī)在高出海面45m的高處,以80m/s的速度水平飛行,為了使飛機(jī)上投下的炸彈落在停在海面上的敵船,應(yīng)該在與轟炸目標(biāo)的水平距離為多遠(yuǎn)的地方投彈?不計(jì)空氣阻力。分析:對(duì)于這道題我們可以從以下幾個(gè)方面來(lái)考慮:(1)從水平飛行的飛機(jī)上投下的炸彈,做什么運(yùn)動(dòng)?為什么?(2)炸彈的這種運(yùn)動(dòng)可分解為哪兩個(gè)什么樣的分運(yùn)動(dòng)?3)要想使炸彈投到指定的目標(biāo)處,你認(rèn)為炸彈落地前在水平方向通過(guò)的距離與投彈時(shí)飛機(jī)離目標(biāo)的水平距離之間有什么關(guān)系?拓展:1、式飛機(jī)在高出海面45m的高處,以80m/s的速度水平飛行,尾追一艘以15m/s逃逸的敵船,為了使飛機(jī)上投下的炸彈正好擊中敵船,應(yīng)該在與轟炸目標(biāo)的水平距離為多遠(yuǎn)的地方投彈?不計(jì)空氣阻力。2、在一次摩托車跨越壕溝的表演中,摩托車從壕溝的一側(cè)以速度v=40m/s沿水平方向向另一側(cè),壕溝兩側(cè)的高度及寬度如圖所示,摩托車可看做質(zhì)點(diǎn),不計(jì)空氣阻力。(1)判斷摩托車能否跨越壕溝?請(qǐng)計(jì)算說(shuō)明(2)若能跨過(guò),求落地速度?

【教學(xué)重點(diǎn)】直線的點(diǎn)斜式方程、斜截式方程的確定.【教學(xué)難點(diǎn)】直線的點(diǎn)斜式方程、斜截式方程的確定.【教學(xué)過(guò)程】1、對(duì)特殊三角函數(shù)進(jìn)行鞏固復(fù)習(xí);表1 內(nèi)特殊三角函數(shù)值 不存在圖1 特殊三角形2、鞏固復(fù)習(xí)直線的傾斜角和斜率相關(guān)內(nèi)容;直線的傾斜角:,;直線的斜率: , ;設(shè)點(diǎn)為直線l上的任意兩點(diǎn),當(dāng)時(shí),
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