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Re: [Phys-L] Buoyancy Questions

It is tempting to suppose that at the moment when each ball is just below the (undisturbed) surface level, the initially deeply submerged ball would have the advantage of upward velocity. But the surface is not undisturbed, so that one ball is lifting a layer of water and the other is lifting a layer of air.

Brian Whatcott Altus OK


On 7/1/2013 10:55 PM, Dan Crowe wrote:
Surface tension has to be a major component. In the first case, surface tension pushes the ball upward; in the second case, surface tension pushes the ball downward.
Daniel Crowe
Loudoun County Public Schools
Academy of Science
dan.crowe@lcps.org
Michael Barr 07/01/13 11:32 PM >>>
I was at my sister's pool a few days ago and I noticed that when I took a
ball (a pool volleyball) and submersed it just below the surface and
released it, the ball would jump around 3 or 4 feel above the surface of
the water. When I pushed the ball deeper, about 2 or 3 feet below the
surface and let go, the ball would rise and then sort of sputter at the
surface and not rise above the surface at all. Does anyone know how to
explain this. I thought it would be a nice challenge for my students but
the problem is, I don't think I know what's going on either.
Thanks in advance.
Mike Barr


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