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Re: [Phys-L] Buoyancy Questions



A quick thought:

When the moving ball is just about to break the surface, the pressure on the lower surface of the ball is probably below the hydrostatic value. Even though there is no longer water to push out of the way above the ball, water has to flow into the space that was just occupied by the upwardly moving ball.

Bob at PC

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Michael Barr
Sent: Monday, July 01, 2013 11:21 PM
To: Phys-l@phys-l.org
Subject: [Phys-L] Buoyancy Questions

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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