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The Turtle
Buoyancy: To Float Or Not To Float
Two Important Principles to Learn First:Archimedes' Principle: Any object completely or partially immersed in a fluid (liquid or gas) is buoyed up by a force equal to the weight of the displaced fluid.
What does this mean?
Everything takes up a certain amount of space. This amount is called volume. When you put an object in a fluid (such as water), the same amount/volume of water must make room, or be displaced, for the object. In a sense, the amount of the object in the water is pushing against the same amount of the water. If the amount of water weighs more, or is more dense, than the object that is immersed, the object floats (learn about density below).
Pascal's Principle: Any change in pressure in a fluid is transmitted undiminished through the fluid.
What does this mean?
If you fill a bottle with water and squeeze it, no matter where you squeeze it from or how hard you squeeze it, every part of the water and everything in it will feel the same amount of squeeze (or pressure).
Density: The Deciding Factor
Density: The object's mass over it's volume (m/V). For example, the density of lead is 11.3 g/cc (check me on this). (Review on Metric Units)
How does this affect buoyancy?
If an object is less dense than the fluid in which it lies, it will float. For example, the helium in a balloon is much less dense than normal air, so the balloon floats (often away if you don't hold on to it).
Now that you know what buoyancy is, and what affects how buoyant an object is, try your hand at controlling buoyancy by clicking here for a submarine demo made using java technology. You get to control the mass and volume of an object to see how it floats. Have fun!
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