Friday, November 30, 2007

Rolling ellipsoid

I saw an ellipsoidal grape rolling around on the subway car floor as the train accelerated and decelerated. It seems paradoxically dynamically more stable flipping end over end over its long axis than rolling around its circular cross section. It first starts rolling around its circular cross section, but if the direction of the force is not aligned the in the same direction of the rolling, then instabilities flip it to end-over-end motion.

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