Topics
Rotational dynamics, Educational aids, Fluid dynamics

In their interesting paper Tuleja et al.1 consider the motion of a plate that is tossed upward with an initial angular velocity around an approximately vertical axis. They describe Feynman’s observations and their own as a combination of a spinning motion and a wobbling motion. The spin is readily observed by following marked points on the rim of the plate, and the wobble is observed by the cyclic changes in the orientation of the plane of the plate. The wobble frequency is observed to be about twice the spin frequency. They present and discuss visualizations of the results of a numerical Lagrangian analysis of the torque-free motion of a thin disc (representing the plate) relative to its center of mass. It is seen that the disk spins around its symmetry axis while the axis precesses uniformly in a small cone at a frequency very close to twice the spin...

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