Fri, May 16, 2008 - Page 20 News List

Weekend Science: Clearing out a borehole 鑽井通通樂

Welcome to Weekend Science! Every Friday we're going to guide you through some cool experiments that you can do at home. It's a good idea for you to keep a record of what you do in a Science Journal. That way you can record what you learn, compare results and maybe use them to design new experiments! Have a look at the Science Journal box for some ideas to get you started. Remember to always ask a grown-up’s permission before trying out an experiment.

歡迎閱讀《週末科學版》!我們每週五都要為你介紹可以在家中進行的有趣科學實驗。你可以在《科學日誌》中記錄自己做了哪些活動,這樣就可以將所學的記錄下來,比較這些結果,也可以利用它們來設計新的實驗!先看一下《科學日誌》的點子再開始吧。展開實驗之前,記得要獲得大人的同意喔!

照片︰Michael Kearney

PHOTO: MICHAEL KEARNEY, TAIPEI TIMES

A lot of rock bits are broken up as a drill bores through the earth. A special system that makes use of drilling mud is used to remove those bits so that they don’t get in the way. Today we’re going to look at why drilling mud needs to have a high viscosity.

What you will need:

A tall cup (this will represent the borehole)

A straw (this will represent the drill bit)

Sand (this will represent the rock bits)

Water (this is a liquid with a low viscosity)

Shampoo (this has a much higher viscosity than water)

► Put some sand into the cup and fill it with water. Wait for the water to penetrate through the sand.

► Place the straw into the cup so that it touches the bottom. Blow for a few seconds and then look at what the sand does.

► Repeat the above steps, but this time use shampoo instead of water. What’s the difference?

(MICHAEL KEARNEY, STAFF WRITER)

鑿孔機在地表鑽洞時,土石會破碎成很多小碎石,這時就會利用一種運用鑽井液的特殊系統來清掉這些碎石,以免它們妨礙鑿孔機工作。今天我們要來看看為什麼需要高黏度的鑽井液。

所需材料︰

一個細高的杯子(用來當作鑽井)

一根吸管(用來當作鑿孔器)

沙子(用來當作碎石塊)

水(不黏稠的液體)

洗髮精(比水黏稠的液體)

► 把一些沙子放入杯中後再加滿水,等水完全滲入底下的沙子。

► 把吸管放入杯中,直到碰到杯底,對著吸管吹氣數秒,然後觀察看看沙子有什麼變化。

► 重複上述步驟,但這次我們用洗髮精取代水,結果會有什麼不同?

(翻譯︰袁星塵)

What's the science? 科學原理

Viscosity describes a liquid’s resistance to flow. Water flows easily, so it has a low viscosity. Shampoo doesn’t flow as easily, so it has a higher viscosity. Drilling mud has to have a high viscosity in order to suspend rock bits so they can be carried upwards.

黏性就是液體流動的阻力。水很容易流動,所以它的黏性很低;洗髮精不容易流動,所以黏性較高。鑽井液的黏性必須很高,才能支撐碎石塊懸浮其中,進而把它們送出井外。

當你用水做實驗時,沙子浮起來沒多久後立刻又沉下去;水的黏性很低,所以沒辦法讓沙礫懸浮在其中。

當你用洗髮精做實驗時,沙子會浮起,但重新下沉的速度卻緩慢�?F洗髮精的黏性高,所以它防止沙子沉回杯底的效果較好。水不能作為很好的鑽井液,但洗髮精應該是種不錯的選擇。

Bonus 你知道嗎

Try dropping a coin into water from about a meter high. Did you notice a splash?

Now try dropping a coin into shampoo from about a meter high. The splash should be much smaller, if there is any at all. The higher a liquid’s viscosity, the more resistant it will be to splashing.

從一公尺高的地方朝著水裡丟一枚硬幣試試看,你注意到濺出的水花了嗎?

接著試著從約一公尺高處朝洗髮精投入一枚硬幣,濺出來的洗髮精應該比水少很多(如果有的話)。液體的黏性愈高,就愈不會濺出來。


Further ideas 進階點子

Cornstarch mixed with water has some strange properties. Its viscosity depends on how much pressure is applied.

Add two parts cornstarch to one part water and stir slowly. Gradually add more water and continue to stir the mixture until it acts like a liquid when you stir it slowly and a solid when you stir it quickly. Try kneading the mixture into a ball. If you continuously apply force to the ball, it will act like a solid, but once you stop applying force, the ball will “melt” before your eyes.

攪拌後的太白粉水有一些奇怪的特性,它的黏性取決於它所受的壓力大小。

用二比一的比例調和太白粉和水後輕輕攪拌,再慢慢加入一些水,持續攪拌;若是你攪拌的速度很慢,它會呈液體狀,但要是你攪拌的速度很快,它就呈固體狀。試試看把混合物搓成一顆小球,如果你持續用力捏它,它就會呈現固態;但是一旦你不再用力,它就會在你面前「溶化」。

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