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(shū)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(jué)類(lèi)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 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.
全班齊讀第五段內(nèi)容。請(qǐng)一位同學(xué)分析,接著讓這位同學(xué)按他分析的讀一遍。3、4兩自然段的平緩之后,第5段作者的情感再次抬升。為了滿足這種情感的張揚(yáng),作一口氣連用了四個(gè)排比句式“現(xiàn)在是……時(shí)候”,一方面這是情感發(fā)泄的需要,另一方面這種排山倒海的語(yǔ)勢(shì)也加強(qiáng)了內(nèi)容的表達(dá),極強(qiáng)地突出了現(xiàn)實(shí)為自由、平等而戰(zhàn)的重要性。四、學(xué)會(huì)演講我們剛才細(xì)讀了課文,但讀和講是有區(qū)別的。所謂演講,是一門(mén)語(yǔ)言藝術(shù),它的主要形式是“講”,即運(yùn)用有聲語(yǔ)言并追求言辭的表現(xiàn)力和聲音的感染力;同時(shí)還要輔之以“演”,即運(yùn)用面部表情、手勢(shì)動(dòng)作、身體姿態(tài)乃至一切可以理解的態(tài)勢(shì)語(yǔ)言,使講話“藝術(shù)化”起來(lái),從而產(chǎn)生一種非凡的藝術(shù)魅力。那么,接下來(lái)就假設(shè)一下假如你是馬丁·路德·金,你會(huì)怎樣去講這篇演講辭。
The activity topic of this section is "report an ongoing event", and the structure is the passive voice of present continuous tense. Rare wild animals are suffering from large-scale poaching, and species are on the brink of danger. Rescue operations are underway. "Being" and "suffering" are the meanings of the present progressive passive voice.The usage of present progressive passive voice is of great importance in writing a good discourse and appreciating some difficult language items, so it is vital to master it and use it flexibly in a context.1. Motivate Ss to deepen the understanding of the usage of present progressive passive voice in a fixed context.2. Enable Ss to master the usage of present progressive passive voice and use it flexibly in a context.3. Lead Ss to construct sentences or appreciate sentences used master it and use it flexibly in a context.1. Help students to appreciate the function of the usage of present progressive passive voice in a sentence2. Instruct students to write essays using the proper usage of present progressive passive voice.Look at the picture and tell me what are workers doing? What is the house being done?
This unit is about the Internet, which has a great influence to our humans and our lives. During the Listening & Speaking & Talking and Reading and Thinking section, the influence in examples has been shown. Thus, use the Present Perfect Tense is appropriate. However, in order to show the justice or weaken the doer of the behavior/action, it’s better to use the Present Perfect Passive Voice than the Present Perfect Tense. Besides, having learned to use the Present Perfect Passive Voice, students can beautify their language in their writing. 1. Learn the structure of the Present Perfect Passive Voice and its functions. 2. Learn to change the sentences with the Present Perfect Passive Voice into the sentences with the Present Perfect Passive Voice. 3. Learn to write sentences with the Present Perfect Passive Voice flexibly according to the context. 1. Learn the structure of the Present Perfect Passive Voice and its functions. 2. Learn to change the sentences with the Present Perfect Passive Voice into the sentences with the Present Perfect Passive Voice. 3. Learn to write sentences with the Present Perfect Passive Voice flexibly according to the context. Step 1 Observe the following sentences, then change the sentences into passive voice.He has been selected to take part in the sports meeting.(肯定句)他已被挑選出來(lái)參加運(yùn)動(dòng)會(huì)。The ink has not been removed from his overcoat.(否定句)墨跡還沒(méi)有從他外套上去掉。
This unit is about history and traditions. From the opening page, we can know that this unit will introduce the history and traditions around the world. As Marcus Garvey says “A people without the knowledge of their past history, origin and culture is like a tree without roots”, it is important for students to realize the importance and value of knowing the history and traditions and their further meanings. And this part ( listening and speaking ) is divided into two parts: Part A---share views on historic sites, Part B ---talk about a visit to a historic tourist destination. By talking with a foreigner, the speakers introduce the historic attractions and their cultures. Part A is that William, a British student, who was going to visit the Confucius Temple and a Chinese student, Xiao Kong, who was going to the Confucius Temple to meet with the members of the research group, went together and exchanged their views on the Confucius Temple, Confucius, Confucius' descendants and Confucius' educational thoughts. Part B is a conversation between Xiao Yan, a youth hostel receptionist and Paul, a backpacker about the feelings and experience after visiting the Chinese famous tourist attraction Pingyao.1. Guide students to understand the content of listening texts in terms of the whole and key details; 2. Cultivate students' ability to guess the meaning of words in listening; discuss with their peers how to talk about historic spots and great person.3. Instruct students to use functional sentences of showing one’s excitement, surprise and disappointment.1. Guide students to understand the content of listening texts in terms of the whole and key details; 2. Cultivate students' ability to discuss with their peers the related topics.3. Enable students to use the functional items of showing one’s excitement, surprise and disappointment.
Features of languages1.Finally, in the 20th century, the southern part of Ireland broke away from the UK, which resulted in the full name we have today: the United Kingdom of Great Britain and Northern Ireland.該句是一個(gè)復(fù)合句。該句主句為:the southern part of Ireland broke away from the UK;which resulted in the full name we have today為which引導(dǎo)的定語(yǔ)從句代指前面整句話的內(nèi)容,we have today為定語(yǔ)從句修飾先行詞name。譯文:最后,在20世紀(jì),愛(ài)爾蘭南部脫離英國(guó),這導(dǎo)致了我們今天有的英國(guó)的全名:大不列顛及北愛(ài)爾蘭聯(lián)合王國(guó)。2.Almost everywhere you go in the UK, you will be surrounded by evidence of four different groups of people who took over at different times throughout history.該句是一個(gè)復(fù)合句。該句主句為:you will be surrounded by evidence of four different groups of people;其中Almost everywhere you go in the UK為讓步狀語(yǔ)從句; who took over at different times throughout history為定語(yǔ)從句修飾先行詞people。譯文:幾乎無(wú)論你走到英國(guó)的任何地方,你都會(huì)發(fā)現(xiàn)歷史上有四種不同的人在不同的時(shí)期統(tǒng)治過(guò)英國(guó)。3.The capital city London is a great place to start, as it is an ancient port city that has a history dating all the way back to Roman times.該句是一個(gè)復(fù)合句。該句主句為:The capital city London is a great place to start; as it is an ancient port city that has a history dating all the way back to Roman times.為原因狀語(yǔ)從句;dating all the way back to Roman times為現(xiàn)在分詞短語(yǔ)作定語(yǔ)修飾history。
(4)Now we have heard a number of outstanding speeches ... 我們已經(jīng)聆聽(tīng)了許多精彩的發(fā)言……(5)Because we wanted the nations of the world, working together, to deal with ... 因?yàn)槲覀兿M澜绺鲊?guó)團(tuán)結(jié)起來(lái)去應(yīng)對(duì)……(6)And if we do not act ... 如果我們不采取行動(dòng)……(7)Now, I share the concerns that have been expressed ... 我也同意對(duì)于……表達(dá)的擔(dān)心(8)Let us show the world that by working together we can ... 讓我們告訴全世界,通過(guò)一起努力我們可以……(9)It is now time for us to ... 是時(shí)候我們……(10)And I have always wished that ... 我一直希望……(11)Thank you for letting me share this day with me.感謝你們和我共度這一天。實(shí)踐演練:假如你是高中生李華,你校將舉辦一次以“音樂(lè)”為主題的演講比賽,請(qǐng)你按照主題,寫(xiě)下你的演講稿。注意:詞數(shù)100左右。First of all, thank you for listening to my speech. My topic is: love music like love yourself.Music is like the air we need to maintain our normal lives around us. You can't imagine how terrible a world without music would be. Movies and TV shows have no music, only dry conversations and scenes; mobile phones only vibrations; streets only noisy crowds; cafes, western restaurants only depressed meals. What a terrible world it is!As a student, I hope we all can enjoy the fun brought by music in our spare time. Instead of just listening to music, we can even make our own music. Let's enjoy the fun of music!Thanks again for your attention!
1. 標(biāo)題首先根據(jù)海報(bào)的特點(diǎn)、格式寫(xiě)明標(biāo)題。海報(bào)中往往把內(nèi)容作為大標(biāo)題。例如: Save the earth, Save the birds。2. 正文部分不同的海報(bào)其正文部分的側(cè)重點(diǎn)不同。對(duì)于介紹性的海報(bào), 首先要引出話題, 其次列出原因, 最后是總結(jié)。對(duì)于宣傳類(lèi)的海報(bào), 要寫(xiě)明具體內(nèi)容, 如: 活動(dòng)內(nèi)容, 地點(diǎn)以及參加活動(dòng)的注意事項(xiàng), 主持或舉辦單位等。1. 圖片: 要選擇引人注目的圖片, 與主題要相關(guān), 色彩明亮。話題句式 1. It is a treasure of our country. 它是我國(guó)的國(guó)寶。2. Believe it or not, at present only several thousand pandas exist in the world. 信不信由你, 目前世界上僅現(xiàn)存幾千只熊貓。 3.It’s because of human activities that tigers are endangered. 正是因?yàn)槿祟?lèi)的活動(dòng), 老虎處于瀕危的狀態(tài)。4. Many wild animals are in danger of dying out. 很多野生動(dòng)物面臨著滅絕的危險(xiǎn)。 5. The government has taken effective measures to protect them. 政府已采取有效的措施來(lái)保護(hù)它們。6. People should raise the awareness of the protection of wild animals. 人們應(yīng)該提高保護(hù)野生動(dòng)物的意識(shí)。 7. It’s amazing that there are merely less than 1, 000 finless porpoises living in China. 非常令人吃驚, 目前中國(guó)僅有不足1 000只江豚。
Paragraph 3. Jan decided to start an IT club to teach old people how to use computers and the Internet. Paragraph 4. Jan has started taking online classes to learn more about how to use the Internet to make society better. Paragraph 5. Jan’s life has been greatly improved by the Internet. Step 5: Critical thinking:(1)How do you arrange your time spent on study and the Internet? Is it reasonable? I usually surf the Internet using my mobile phone for only an hour after class, and it is reasonable for me.(2)What are your online activities? Are they safe? I chat with my friends, read news and play games. I never give away my private information so I think they are safe.Step 4: summary Much has been written about the wonders of the World Wide Web. There are countless articles (1)______(tell) us how the Internet has made our lives more convenient. But the Internet has done a lot (2)_____(much) for people than simply make life more convenient. People’s lives (3) _________________(change) by online communities and social networks so far. Take Jan for example, who developed a serious illness that made her (4)_____(stick) at home with only her computer to keep (5)___(she) company. She joined an online group (6)______ she could share problems, support and advice with others. She considered the ability to remove the distance between people as one of the greatest (7)_______(benefit). She was so inspired (8)____ she started an IT club in which many people have been helped. She has started to learn more about how to use the Internet to make society better. Her next goal is to start a charity website to raise money (9)___ children in poor countries. Jan’s life has been (10)______(great) improved by the Internet. Step 5 Homework:Review what we have learned and find out the key language points in the text.
山西省總結(jié)出了許多重點(diǎn)工礦區(qū)的生態(tài)環(huán)境建設(shè)模式,即圍繞煤田的露天開(kāi)采區(qū)、居民點(diǎn)和主要交通線建設(shè)區(qū),通過(guò)工程及生物措施,結(jié)合土地的復(fù)墾,充分利用廠礦的人力、財(cái)力和科技優(yōu)勢(shì),建立集約經(jīng)營(yíng)的高效蔬菜、水果及肉蛋奶生產(chǎn)基地(圖3.13)。1.說(shuō)一說(shuō)圖中各種工程及生物措施的作用。點(diǎn)撥:參考圖3.13圖中各工程及措施的作用:(1)隔離護(hù)壩:主要作用是將采掘區(qū)與河流隔開(kāi),以免河水流入采掘區(qū)。(2)排水溝:主要作用是引開(kāi)可能進(jìn)入采掘區(qū)的雨水或其他水源。(3)公路緊靠采掘區(qū),方便運(yùn)輸車(chē)輛就近從工地上公路。(4)“固沙草方格”,即在流沙表面用麥草、稻草扎成1×1米的草方格,使流沙不易被風(fēng) 吹起,達(dá)到阻沙、固沙的目的,并在草方格上栽種沙蒿、花棒、籽蒿、擰條等沙生植物,建立起旱生植物帶,營(yíng)造擋沙樹(shù)林。
2.通過(guò)西氣東輸輸送到上海的天然氣,價(jià)格只相當(dāng)于進(jìn)口天然氣的3/4、同等熱值煤氣的 2/3。你認(rèn)為是否應(yīng)該提高天然氣的價(jià)格,以促進(jìn)西部的發(fā)展。點(diǎn)撥:可以從不同方面分析。⑷對(duì)環(huán)境的影響①有利于改善東部地區(qū)的大氣質(zhì)量據(jù)監(jiān)測(cè)顯示,在同等熱值的情況下,與煤炭相比,利用天然氣作燃料幾乎不產(chǎn)生二氧化硫、粉塵等污染物質(zhì),氮氧化物和二氧化碳的排放量也大為減少。長(zhǎng)江三角洲地區(qū)的能源長(zhǎng)期高度依賴(lài)煤炭,例如,上海市煤炭消費(fèi)量占能源消費(fèi)總量的70%。從西部地區(qū)輸送來(lái)的天然氣,可以部分替代煤炭。②為了最大限度減少對(duì)沿線地區(qū)生態(tài)環(huán)境的影響,西氣東輸工程在建設(shè)過(guò)程中,嚴(yán)格環(huán)境保護(hù)的要求。③在沿線農(nóng)村地區(qū)推廣使用天然氣,可減少農(nóng)民對(duì)薪柴的需求,從而緩解因植被破壞而帶來(lái)的環(huán)境壓力。
1.用CAI課件模擬汽車(chē)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(chē)),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(chē)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(chē)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(chē)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(chē)跨越壕溝的表演中,摩托車(chē)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(chē)可看做質(zhì)點(diǎn),不計(jì)空氣阻力。(1)判斷摩托車(chē)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?
3.進(jìn)一步體會(huì)力是產(chǎn)生加速度的原因,并通過(guò)牛頓第二定律來(lái)理解勻速圓周運(yùn)動(dòng)、變速圓周運(yùn)動(dòng)及一般曲線運(yùn)動(dòng)的各自特點(diǎn)。(三)、情感、態(tài)度與價(jià)值觀1.在實(shí)驗(yàn)中,培養(yǎng)學(xué)生動(dòng)手、探究的習(xí)慣。2.體會(huì)實(shí)驗(yàn)的意義,感受成功的快樂(lè),激發(fā)學(xué)生探究問(wèn)題的熱情、樂(lè)于學(xué)習(xí)的品質(zhì)。教學(xué)重點(diǎn)1.體會(huì)牛頓第二定律在向心力上的應(yīng)用。2.明確向心力的意義、作用、公式及其變形,并經(jīng)行計(jì)算。教學(xué)難點(diǎn)1.對(duì)向心力的理解及來(lái)源的尋找。2.運(yùn)用向心力、向心加速度的知識(shí)解決圓周運(yùn)動(dòng)問(wèn)題。教學(xué)過(guò)程(一)、 引入新課:復(fù)習(xí)提問(wèn):勻速圓周運(yùn)動(dòng)的物體的加速度——向心加速度,它的方向和大小有何特點(diǎn)呢?學(xué)生回答后進(jìn)一步引導(dǎo):那做勻速圓周運(yùn)動(dòng)物體的受力有什么特點(diǎn)呢?是什么力使物體做圓周運(yùn)動(dòng)而不沿直線飛出?請(qǐng)同學(xué)們先閱讀教材
三、教師總結(jié):在那如火如荼的苦難歲月,梁任公的政治主張屢屢因時(shí)而變,但為人處世的原則始終未變,他不是馮自由等人所描述的那種變色龍。他重感情,輕名利,嚴(yán)于律己,坦誠(chéng)待人。無(wú)論是做兒子、做丈夫、做學(xué)生,還是做父親、做師長(zhǎng)、做同事,他都能營(yíng)造一個(gè)磁場(chǎng),亮出一道風(fēng)景。明鏡似水,善解人意是他的常態(tài),在某些關(guān)鍵時(shí)刻,則以大手筆寫(xiě)實(shí)愛(ài)的海洋,讓海洋為寬容而定格,人間為之增色。我敢斷言,在風(fēng)云際會(huì)和星光燦爛的中國(guó)近代人才群體中,特別是在遐邇有知的重量級(jí)歷史人物中,能在做人的問(wèn)題上與梁?jiǎn)⒊仍囌呤遣淮笕菀渍业降?。四、課后作業(yè):找出文中細(xì)節(jié)及側(cè)面描寫(xiě)的地方,想一想這樣寫(xiě)有什么好處,總結(jié)本文的寫(xiě)作特點(diǎn)。五、板書(shū)設(shè)計(jì):梁任公演講特點(diǎn):
在經(jīng)濟(jì)水平較高、工業(yè)地域規(guī)模較大的地區(qū),其發(fā)展?jié)摿瓦h(yuǎn)不一樣,如鋼鐵工業(yè)。鋼鐵工業(yè)的生產(chǎn)過(guò)程比較復(fù)雜(如課本圖5.31),需要有相互接近的工廠,不僅包括從事鋼鐵生產(chǎn)各道工序的工廠,如燒結(jié)廠、焦化廠、煉鐵廠、煉鋼廠、軋鋼廠,還包括與鋼鐵生產(chǎn)有聯(lián)系的工廠,如氧氣廠、機(jī)修廠、發(fā)電廠、水泥廠等,總共可達(dá)20~30個(gè)工廠。這些工廠集 聚,設(shè)備大,管線長(zhǎng),占地多。因此,這樣形成的工業(yè)地域(鋼鐵工業(yè)區(qū))面積廣,發(fā)育程度高,發(fā)展?jié)摿Υ?。這類(lèi)工業(yè)地域 再加上為方便眾多工人生活所配置的服務(wù)業(yè)和其他工業(yè),在發(fā)展過(guò)程中,往往由于工業(yè)地域的擴(kuò)展而形成工業(yè)城市。例如,我國(guó)的鞍山(“鋼都”)、攀枝花、馬鞍山、包頭(“草原鋼城”)等鋼鐵工業(yè)城市的形成。除此之外,石油化工區(qū)、機(jī)械制造工業(yè)區(qū)等屬于發(fā)育程度高的工業(yè)地域,也往往擴(kuò)展而形成工業(yè)城市。例如,我國(guó)的石油城大慶、克拉瑪依,汽車(chē)城十堰等。
四、速度和速率學(xué)生閱讀教材第18頁(yè)相應(yīng)部分的知識(shí)點(diǎn),讓學(xué)生總結(jié).生:速度既有大小,又有方向,是矢量,速度的大小叫速率,教師引導(dǎo)學(xué)生看教材第18頁(yè)圖1.3—2.觀察汽車(chē)的速度計(jì),討論后說(shuō)出你從表盤(pán)上獲取的有用信息。生:汽車(chē)的速率.指針指在相應(yīng)數(shù)字的瞬間,就表示汽車(chē)在那一瞬時(shí)的速率是那個(gè)值.生:還可以從表盤(pán)上直接讀出公里里程.師:日常生活中的“速度”有時(shí)指速度,也有時(shí)指速率,要看實(shí)際的物理情景。[討論與交流]甲、乙兩位同學(xué)用不同的時(shí)間圍繞操場(chǎng)跑了一圈,都回到了出發(fā)點(diǎn),他們的平均速度相同嗎?怎樣比較他們運(yùn)動(dòng)的快慢?學(xué)生討論,體驗(yàn)平均速度的缺陷,引入平均速率。生1:位移都是零,平均速度等于位移跟發(fā)生這段位移所用時(shí)間的比值,所以他們的平均速度都是零。生2:即使一位同學(xué)站在原地不跑,他的平均速度也是零啊,可我們運(yùn)動(dòng)會(huì)上不是這樣比快慢的,如果這樣,那多不公平啊?
1.加速度與力的關(guān)系:實(shí)驗(yàn)的基本思路是保持物體的質(zhì)量不變,測(cè)量物體在不同的力的作用下的加速度,分析加速度與力的關(guān)系。有了實(shí)驗(yàn)的基本思路,接下去我們就要準(zhǔn)備實(shí)驗(yàn)器材,以及為記錄實(shí)驗(yàn)數(shù)據(jù)而設(shè)計(jì)一個(gè)表格。為了更直觀地判斷加速度與力的數(shù)量關(guān)系,我們以 為縱坐標(biāo)、 為橫坐標(biāo)建立坐標(biāo)系,根據(jù)各組數(shù)據(jù)在坐標(biāo)系中描點(diǎn)。如果這些點(diǎn)在一條過(guò)原點(diǎn)的直線上,說(shuō)明 與 成正比,如果不是這樣,則需進(jìn)一步分析。2.加速度與質(zhì)量的關(guān)系:實(shí)驗(yàn)的基本思路是保持物體所受力不變,測(cè)量不同質(zhì)量的物體在該力作用下的加速度,分析加速度與質(zhì)量的關(guān)系。有了實(shí)驗(yàn)的基本思路,接下去我們就要準(zhǔn)備實(shí)驗(yàn)器材,以及為記錄實(shí)驗(yàn)數(shù)據(jù)而設(shè)計(jì)一個(gè)表格。為了更直觀地判斷加速度與質(zhì)量的數(shù)量關(guān)系,我們以 為縱坐標(biāo)、 為橫坐標(biāo)建立坐標(biāo)系,根據(jù)各組數(shù)據(jù)在坐標(biāo)系中描點(diǎn),根據(jù)擬合的曲線形狀,初步判斷 與 的關(guān)系是反比例函數(shù)。再把 圖像改畫(huà)為 圖像,如果是一條過(guò)原點(diǎn)的斜直線,說(shuō)明自己的猜測(cè)是否正確。
生:還可以從表盤(pán)上直接讀出公里里程.師:日常生活中的“速度”有時(shí)指速度,也有時(shí)指速率,要看實(shí)際的物理情景。[討論與交流]甲、乙兩位同學(xué)用不同的時(shí)間圍繞操場(chǎng)跑了一圈,都回到了出發(fā)點(diǎn),他們的平均速度相同嗎?怎樣比較他們運(yùn)動(dòng)的快慢?學(xué)生討論,體驗(yàn)平均速度的缺陷,引入平均速率。生1:位移都是零,平均速度等于位移跟發(fā)生這段位移所用時(shí)間的比值,所以他們的平均速度都是零。生2:即使一位同學(xué)站在原地不跑,他的平均速度也是零啊,可我們運(yùn)動(dòng)會(huì)上不是這樣比快慢的,如果這樣,那多不公平啊?師:平均速度v=Δx/Δt,甲、乙的位移都為零,所以他們的平均速度也都等于零.在這里平均速度無(wú)法顯示他們運(yùn)動(dòng)快慢的不同,要用到另一物理量:平均速率.平均速率等于物體運(yùn)動(dòng)通過(guò)的路程跟所用時(shí)間的比值.他們兩人通過(guò)的路程相同且都不為零,但所用時(shí)間不同.顯然用時(shí)短的運(yùn)動(dòng)得快,也就是平均速率大.生:這不是我們初中學(xué)過(guò)的速度嗎?