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Does a wooden ball, of the same size as the mostly-air ball, exhibit the same behavior? If not then the role of gravity is important (the buoyant force being nearly the same). That seems to be an experiment worth performing.
Another parameter worth changing is the size of the mostly-air ball. Do balls of different size behave in the same way? Experiments designed to answer such questions, first qualitatively and then quantitatively, are worth performing. They offer a chance to do what scientist do, when they try to understood what happens.
Ludwik Kowalski
http://csam.montclair.edu/~kowalski/life/intro.html
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On Jul 2, 2013, at 2:49 PM, John Clement wrote:
It has to be something unique to having been far underwater. So a
reasonable hypothesis is that there is still water on the upper side as it
comes out, which adds to the weight and makes decreases the net force on the
ball as it comes out. This might be testable if you take a video of it.
You may see that as the ball emerges there is still a significant layer of
water on top of it when you push it far underwater. The surface tension has
nothing to do with it because it is underwater in both cases. While fluid
friction comes into play, near the surface this effect should be same no
matter how deep you push it initially.
So take the video and see what is happening!
John M. Clement
Houston, TX
I was at my sister's pool a few days ago and I noticed that when Ifeel above
took a ball (a pool volleyball) and submersed it just below the
surface and released it, the ball would jump around 3 or 4
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 andthen sort
of sputter at the surface and not rise above the surface atall. Does
anyone know how to explain this. I thought it would be a niceI know what's going on either.
challenge for my students but the problem is, I don't think
Thanks in advance._______________________________________________
Mike Barr
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Forum for Physics Educators
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_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l
_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l