技术文库

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  What was the polite request?

  If you park your car in the wrong place, a traffic policeman will soon find it. You will be very lucky if he lets you go without a ticket. However, this does not always happen. Traffic police are sometimes very polite. During a holiday in Sweden, I found this note on my car: ‘sir, we welc ...

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  What was the good news?

  The secretary told me that Mr. Harmsworth would see me. I felt very nervous when I went into his office. He did not look up from his desk when I entered. After I had sat down, he said that business was very bad. He told me that the firm could not afford to pay such large salaries. Twenty people ...

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  Did the young man speak English?

  I had an amusing experience last year. After I had left a small village in the south of France, I drove on to the next town. On the way, a young man waved to me. I stopped and he asked me for a lift. As soon as he had got into the car, I said good morning to him in French and he replied in the ...

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  Why will the police have a difficult time?

  The Greenwood Boys are a group of pop singers. At present, they are visiting all parts of the country. They will be arriving here tomorrow. They will be coming by train and most of the young people in the town will be meeting them at the station. Tomorrow evening they will be singing at the Wor ...

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  Where is Captain Alison going and how?

  Our neighbour, Captain Charles Alison, will sail from Portsmouth tomorrow. We’ll meet him at the harbour early in the morning. He will be in his small boat, Topsail. Topsail is a famous little boat. It has sailed across the Atlantic many times. Captain Alison will set out at eight o’ ...

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  Who paid for Tony’s dinner?

  I was having dinner at a restaurant when Tony Steele came in. Tony worked in a lawyer’s office years ago, but he is now working at a bank. He gets a good salary, but he always borrows money from his friends and never pays it back. Tony saw me and came and sat at the same table. He has nev ...

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  What happened to the clavichord?

  We have an old musical instrument. It is called a clavichord. It was made in Germany in 1681. Our clavichord is kept in the living room. It has belonged to our family for a long time. The instrument was bought by my grandfather many years ago. Recently it was damaged by a visitor. She tried to ...

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  Why did the writer complain to the people behind him?

  Last week I went to the theatre. I had a very good seat. The play was very interesting. I did not enjoy it. A young man and a young woman were sitting behind me. They were talking loudly. I got very angry. I could not hear the actors. I turned round. I looked at the man and the woman angrily. T ...

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  生活中的物理-民航飞机的飞行高度

  中型以上的民航飞机都在高空飞行，此处的高空是指海拔7000-12000米的空间。在这个空间以1千米为1个高度层，共分为6个高度层：7千、8千米、9千米、1万米、1万1千米和1万2千米。高空飞行的飞机只允许飞以上给定高空。 　　另外，民航飞机在飞行时，以正南正北方向为零度界限，凡航向偏右(偏东)的飞机飞双数高度层，即8千米、1万米、1万2千米高度层；凡航向偏左(偏西)的飞机飞单数高度层，即7千米、9千米、1万1千米高度层。 　　例如：民航飞机从北京飞往杭州，杭州位于北京南面偏东方向，飞机段飞双数高度层，回程则飞单数层。又如飞机从沈阳飞往杭州，杭州在沈阳的南面偏西方向飞机须飞单数高度层， 回程则飞 ...

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  生活中的物理-清洁能手-吸尘器

  吸尘器能将地面、墙壁、床铺及家用电器等室内用具上的微尘细屑都吸得干干净净，并且连地上的蚂蚁也难逃罗网。　　吸尘器又称真空吸尘器。它有一个电动抽风机，通电后高速运转，使吸尘器内部形成瞬间高真空，吸尘器内的气压大大低于外界的气压。在这个压差作用下，使外界被吸嘴搅打起来的尘埃和脏物伴随气流进入吸尘器桶体内，再经过过滤器即集尘袋的过滤，尘垢留在集尘袋，净化后的空气则经过电动机重新逸入室内。起到冷却电机、净化空气的作用。　　　吸尘器配上不同用途的附件，可完成不同的工作。配上地板刷，可清扫地面。装上扁毛刷，可清扫沙发面、床单、窗帘、毛呢服装及被絮上的灰尘，也可用于清洁纱窗、门窗、灯罩、镜框、书架图书、 ...

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  生活中的物理-天空中飞行的船 – 飞艇

  在1783年发明了气球之后，人们马上就想方设法推进和驾驶气球。　　1784年，法国罗伯特兄弟制造了一艘人力飞艇，长15.6米，最大直径9. 6米，充氢气后可出现1000多公斤的升力。罗伯特兄弟以为，飞艇在空中飞行和鱼在水中游动差不多，因此，把它制成鱼形，艇上装上了浆，这桨是用绸子绷在直径2米的框子上制成的。 　　7月6日进行试飞，当气囊充满氢气后，飞艇冉冉上升，伴随高度的增加，大气压逐渐降低，囊内氢气膨胀，气囊越胀越大，眼看就要胀破，这可把罗伯特兄弟吓坏了，他们赶紧用小刀把气囊刺了一个小孔，才使飞艇安全降到了地面。　　这次试验启示人们，应当在气囊上留一个放气阀门。2个月后，兄弟俩又对飞艇进行了 ...

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  生活中的物理-雨衣上的学问

  下雨天，外出的人们不是打伞，就是穿雨衣。　　雨衣为啥不透水呢？奥妙就在制作材料上。就拿布制雨衣来说吧，它是用防雨布（经过防水剂处理的普通棉布）制成的。防水剂是一种含有铝盐的石蜡乳化浆。石蜡乳化以后，变成细小的粒子，均匀地分布在棉布的纤维上。石蜡和水是合不来的、水碰见石蜡，就形成椭圆形水珠，在石蜡上面滚来滚去。可见，是石蜡起了防雨的作用。物理学上把这种不透水的现象，叫做“不浸润现象”。而水一旦遇到普通棉布，就通过纤维间的毛细管渗透进去，这就叫做“浸润现象”。　　物体是由分子组成的。同一种物质的分子之间的相互作用力，叫做内聚力；而不同物质的分子之间的相互作用力，叫做附着力。在内聚力小于附着力 ...

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