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

[brian whatcott <betwys1@sbcglobal.net>]

 On 10/19/2010 7:19 PM, M. Horton wrote:
> /snip/
> 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?
/snip/
> Mike

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