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.


照片︰Michael Kearney


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?









► 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?


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.




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.



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.



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