英語(yǔ)聽(tīng)力文摘 無(wú)形的力量

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https://online2.tingclass.net/lesson/shi0529/0007/7643/420.mp3

https://image.tingclass.net/statics/js/2012

無(wú)形的力量

A: What's going on?

B: Check out the setup , Yaoyao.

A: A stove, an empty aluminum soda can, kitchen tongs, and a saucepan. Are you experimenting with a new recipe?

B:No, i'm experimenting with air pressure.

A:How?

B:First, i will put about a tablespoon of water in the soda can, and a little cold water in the saucepan. Now, I will heat the water in the soda can on the stove until it boils.

A: There steam coming out of the can.

B: Good! Now watch, i will pick up the can with a kitchen tongs like this and put it face down in the cold water in the pan. Ready?

A:Ready!

B:Here goes!

A: Wow, the can collapse like with being crushed down by an invisible hand.

B: When the water in the can boiled, the water vapor pushed all the air out of the can. And when I flipped the can and put it in the pan, the cold water cooled the vapor, making it condense.

A:Which left the can empty inside, allowing the pressure of the air outside the can to crush it.

B: Exactly. Normal air pressure is about 15 pounds per square inch. Since the can was about three inches high and two inches wide, the air pressure on it was 15 pounds per six inches, or ninety pounds of air pressure used to crush the can.

A: Very interesting!

A:發(fā)生什么事了?

B:瑤瑤，看一下都有些什么設(shè)備吧!

A:火爐，鋁制的的易拉罐，餐鉗和平底鍋。你是在做一個(gè)新的食譜嗎?

B:不是的，我是在做一個(gè)關(guān)于氣壓的實(shí)驗(yàn)。

A:怎么做?

B:我先在易拉罐里加入約一湯匙的水，在平底鍋里加少許冷水。接著，將易拉罐放在火爐上加熱至其沸騰。

A:這樣水蒸汽就從罐子里冒出來(lái)了。

B:對(duì)了!現(xiàn)在，我要用餐鉗像這樣將易拉罐夾起來(lái)，并將其正面放在有冷水的平底鍋里。準(zhǔn)備好了嗎?

A:準(zhǔn)備好了!

B:看看會(huì)發(fā)生什么吧!

A:哇噢，易拉罐碎了!就像被一只無(wú)形的手給壓碎的!

B:因?yàn)樵?易拉罐里的)水沸騰時(shí)，罐子里的所有空氣都被水蒸汽排出。所以當(dāng)我將罐子翻轉(zhuǎn)過(guò)來(lái)放在平底鍋里時(shí)，(鍋里的)冷水將水蒸汽冷卻、凝結(jié)。

A：這就使得易拉罐內(nèi)部變空，從而讓外面的氣壓將其粉碎。

B：非常正確!正常的氣壓大約是每平方英寸15磅。由于易拉罐大約是3英寸高、2英寸寬，它周?chē)臍鈮壕褪?平方英寸15磅，即每平方英寸90磅，從而將易拉罐粉碎。

A:太有意思了!