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Re: [Phys-l] Definition of upthrust or buoyancy

On 10/19/2010 7:19 PM, M. Horton wrote:
Where does the buoyant force come from? Or to ask it in a slightly
different way, what causes the buoyant force on an object and how?

I'll bite. There is a force (as we usually model it) that attracts objects towards nearby massy objects.
Apples head off in one particular direction, and so does water.
There is a competition for realizing this displacement, which varies in some contexts, with density.
As objects jostle each other in getting down, they can exert pressure on each other.
When a solid jostles with a liquid, each applies pressure on the other. For a given
interface pressure, the less dense object loses the competition, allowing the more dense liquid
to descend preferentially.
Like that?

Brian W