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Q & A: Floating in Water....sometimes

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Most recent answer: 10/22/2007
Q:
why does an egg float in salt water
- Anonymous
A:
The big difference between salt water and regular water is that salt water is more dense than regular water. That means that every bit of salt water weighs more than regular water. That makes sense because we've added extra salt to the mix.

The next step is how things float. The easiest way to remember if something floats is to think about how much water it displaces. So if we take the volume of the egg and take that much water, which weighs more? The salt water will weigh more than the egg. This means that if the whole egg were under the surface of the water, the water will push up on the egg more than gravity pulls down on the egg. The result of this is that the egg gets pushed up to the surface, and will float with a slight fraction of its volume above the level of the water. In fact, it will float is such a way that it has displaced a volume of water whose mass is exactly equal to the egg's mass.


Incidently, the regular water weighs less than the egg, so the egg will sink to the bottom.


Adam

(published on 10/22/2007)

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