Re: [Phys-L] Nice question on buoyance and balance

[Philip Keller <pkeller@holmdelschools.org>]

Driving to work this morning, I had another thought about this problem (the
original one that started the thread).  I was thinking about how to present
it to my students.  Since the goal is not to stump them with puzzles, I
think I would first ask them about the variation where the ping pong ball
is held in place by the dowel.  I believe that one is easier to understand.
 Same amount of water exerting same buoyancy force on both sides of balance.

Then I would go back and take another look at the question about the
window-washer held by a rope which goes over a pulley and comes back down,
in one case to the window washer and in another case to a hook coming out
of the building.  The tension in the first case is half that of the second.
 Ropes are not magical, free-floating force providers.  There has to be
something at the other end, also experiencing tension.

Then I would go back to the ping pong ball and replace the dowel with a
rope tied  to the bottom of the beaker.

Presented in this order, it is not as much of a puzzle, which is fine with
me.


On Wed, Jan 29, 2014 at 9:28 PM, John Clement <clement@hal-pc.org> wrote:

> As I said in the second message, OOPS.  Write in haste repent in leisure.
> Remember "Independence Day".
> It is always wise to look at all messages and read thoroughly before
> writing.
>
> John M. Clement
> Houston, TX
> > Carl specified an UNtethered ping pong ball.
> > Are you of the same opinion still?
>
>
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