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Q & A: Flowing Water

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Most recent answer: 10/22/2007
Q:
I am working on a science project. I want to see which shape will flow through water the fastest. I have cut out shapes and am running them through a gutter to time them. I need to do research on this subject, but can not find anything. Is this physics? I’ve looked for information about friction, motion, and force. Can you help me?
- Randy Ray (age 11)
First Baptist School, CorpusChristi, TX
A:
Yes, this is physics. In fact, it is a field so big that it is almost its own science. This subject is called fluid dynamics. The reason it was hard to find information is that flowing water is not an easy thing to understand. You would think that it is not that difficult, but since it deals with a liquid instead of a solid, everything becomes more complicated.

There is still friction in when water flows. That friction is called "viscosity". The thicker a liquid is, the slower it moves. That's why pancake syrup moves slowly across your plate while water would move much faster.

You may think that the motion of the water is only to flow down hill, but there is also something called Brownian Motion. That basically means that even when you have a glass of water just sitting on a table, the water inside is moving.

To see this, put a glass of water on a table and let it settle. Then drop a single drop of food coloring into the water. You will see that the color spreads out and eventually fills the whole glass. That's because the water is moving inside the glass.


Adam

(published on 10/22/2007)

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