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The Mysterious Gravity-Defying Aggie Class Ring
Posted: Fri Nov 09, 2012 6:46 pm
by WildBill
For all you Aggies -
At rest, the heavy side of the ring sits on the top of the table. When the ring is spinning, the heavy side goes to the top. Can you explain why this happens?
[youtube]
http://youtube.com/watch?v=EbN8ObCWZsw[/youtube]
Re: The Mysterious Gravity-Defying Aggie Class Ring
Posted: Fri Nov 09, 2012 9:11 pm
by jimlongley
One theory is that the heavy side has a larger contact surface which, when friction causes precession and instability, preserves the rotational energy of the object by flipping the small end down. Check out YouTube videos of Tippe Tops.
Re: The Mysterious Gravity-Defying Aggie Class Ring
Posted: Fri Nov 09, 2012 9:21 pm
by texasmusic
It has to do with moment of inertia of the ring combined with gyroscopic effects and the interaction with the surface.
From Wiki on spin-stabilized sattelites:
The easiest form of attitude stabilization is to give the rigid body an initial spin around an axis of minimum or maximum moment of inertia. The body will then have a stable rotation in inertial space.
AKA the ring is only stable spinning in two directions: the axis shown in the video and the axis pointing through where a finger would be. Since the ring isn't balanced about the second axis, and the face of the ring tends to flop it over, it always reverts to the stable mode.