Re: [Phys-l] Space Balloon

["Bob Sciamanda" <trebor@winbeam.com>]

Let me add that the demo is more demonstrative if there are two tethered 
objects in each closed, glass container. One object is "heavier than water" 
and wants to sink - it is tethered to the top of the container.  The second 
is "lighter than water" and wants to float - it is tethered to the bottom of 
the container.  The tethers are short enough so that the two objects do not 
interfere with each other.  When the container is accelerated in a given 
direction, the heavier object moves in the opposite direction, while the 
lighter object moves in the direction of the acceleration.  On a rotating 
frame, the hanging weight moves to the outside, the floating bob moves 
toward the center of rotation. Very impressive to the discovering student.

Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
http://www.winbeam.com/~trebor/
trebor@winbeam.com
----- Original Message ----- 
From: "LaMontagne, Bob" <RLAMONT@providence.edu>
To: "Bob Sciamanda" <trebor@winbeam.com>; "Forum for Physics Educators" 
<phys-l@carnot.physics.buffalo.edu>
Sent: Wednesday, February 21, 2007 12:21 PM
Subject: Re: [Phys-l] Space Balloon


> . .
> The rotating jars demonstration with fishing floats or candle flames
> gives totally unambiguous verification of this effect. It's very
> counterintuitive for the students and really gets them thinking about
> what centripetal force really means.
>
> Bob at PC