Does Archimedes' principle work in absence of gravity?

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Offline thedoc

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Aman Sharma  asked the Naked Scientists:
Does Archimedes' principle work in absence of gravitational force or space also?

What do you think?
« Last Edit: 17/07/2012 21:30:02 by _system »


Offline evan_au

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Re: Does Archimedes' principle work in absence of gravity?
« Reply #1 on: 20/07/2012 12:48:45 »
Archimedes' Principle is expressed in terms of a less-dense object (like a boat) being partially submerged in a denser fluid, causing it to float. The mass of displaced fluid equals the mass of the floating object.

Archimedes' probably could not envisage an environment where both the water and the boat would float in air!

Archimedes' principle is an application of a more general principle that systems seek the lowest energy state (all other things being equal). On the earth's surface, a boat partially sinking into the water is a lower energy state than either a boat floating above the water, or a watertight boat completely submerged in the water.

However, when the water and the boat are both in orbit, there is no energy difference between the boat floating "above" the water, or totally submerged in it (ignoring surface tension). So there is no lower energy state in which Archimedes Principle could work.

To create such an energy difference, you could spin the experiment, and so centrifugal force substitutes for gravity, and Archimedes Principle will work.