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Why does a Ship Float ?

All boats can float, but floating is more complex and confusing than it sounds and it's best discussed through a scientific concept called buoyancy, which is the force that causes floating. Any object will either float or sink in water depending on its density (how much a certain volume of it weighs). If it's more dense than water, it will usually sink; if it's less dense, it will float. It doesn't matter how big or small the object is: a gold ring will sink in water, while a piece of plastic as big as a football field will float. The basic rule is that an object will sink if it weighs more than exactly the same volume of water. But that doesn't really explain why an aircraft carrier (made from dense metal) can float, so let's explore a bit further.

Buoyancy is easiest to understand thinking about a submarine. It has diving planes (fins mounted on the side) and ballast tanks that it can fill with water or air to make it rise or fall as it needs to. If its tanks are completely filled with air, it's said to be positively buoyant: the tanks weigh less than an equal volume of water and make the sub float on the surface. If the tanks are partly filled with air, it's possible to make the submarine float at some middle depth of the water without either rising up or sinking down. That's called neutral buoyancy. The other option is to fill the tanks completely with water. In that case, the submarine is negatively buoyant, which means it sinks to the seabed. 





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