Re: MOMENT OF INERTIA

[Glenn Knapp <kahuna@VCN.COM>]

At 05:00 AM 12/18/98 -0800, Dan Burns wrote:

>If you run out of experiments to do try this one suggested at our last local

>AAPT meeting:

>

>Roll two identical soft drink cans down a ramp, they reach the bottom at the

>same time. Then shake one up and repeat the race. They do not tie, the shook

>up one is slower! Any explanations?

>

>Dan Burns

>Los Gatos High School

This seems to be a variation of the soda can versus the frozen soda can race down the plane demo demo.  The idea being that the frozen can of soda has a greater moment of inertia becuase the frozen soda rotates with the can.  The liquid soda can has far less angular inertia because the liquid does not rotate - except for a thin layer next to the inner surface of the can.  I would think that the shook up soda can would have bubbles of carbon dioxide clinging to its side.  These bubbles, when the can began to rotate, would cause more of the liquid to rotate - sort of grabbing liquid.  This would give the can a greater anular inertia and cause it to roll down the ramp slower.

Glenn (in Wyoming where we finally got some snow!)

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