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

Thanks John. I want to be sold on the momentum flow method so I am trying to see what the advantage of it is. The short version of the force method would be, "add the mass of a table-tennis ball to the left (the internal forces don't matter) and push down hard on the right--the right goes down." I got the impression that a short movie with little down arrows flowing into and out of the beakers flashed into your mind and you immediately saw the little down arrows flowing into the beaker on the right faster. I wanted to see that movie.

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of John Denker
Sent: Wednesday, January 29, 2014 4:35 PM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] Nice question on buoyance and balance

On 01/29/2014 01:15 PM, Jeffrey Schnick wrote:
Could you please spell out your complete momentum flow argument
leading up to and including the statement that the right side goes
down.

Start with the steel ball suspended above the water. All the momentum is
accounted for: The crane supports the ball and the scale supports the beaker
+ water.

Now lower the ball into the water. The crane now supports one
displacement-worth less weight. By process of elimination, the scale now
supports one displacement-worth more.

The ping-pong ball is chump change.

What am I missing? I could be missing something. I solve these things
subconsciously, far removed from any attentive, sequential, conscious
process. It's a bit like an archaeological dig to go back and try to figure out
what happened. It's hard to describe it in logical, sequential terms.


=================
For extra credit:

Note that the weight of the steel ball doesn't actually matter, only the
displacement. Oddly enough, the displacement of the ping-pong ball doesn't
matter, only its weight. As long as the displacement of the steel ball exceeds
the weight of the ping-pong ball, the thing tilts.
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