Liquids are found in various places. Lakes and oceans have water. Pipes may have water, oil or chemicals in them. Liquid may be contained in a tank or behind a dam.

When something acts on the liquid, like a boat propeller, there are rules and laws for the behavior (actions) of the fluid or liquid. This is called hydrodynamics. Engineers must know what the liquids will do when they build boats, dams or pipes.

Boats moving through water follow some of the same rules as airplanes going through the air. But, aerodynamics is about "air" or gases and hydrodynamics is about water, or liquid.

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Last modified: Sat Jun 20 21:18:09 PDT 1998