Tennis racket theorem: Difference between revisions

Revision as of 23:00, 27 April 2023

Revision as of 23:00, 27 April 2023

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When the body is not exactly rigid, but can flex and bend or contain liquid that sloshes around, it can dissipate energy through its internal degrees of freedom. In this case, the body still has constant angular momentum, but its energy would decrease, until it reaches the minimal point. As analyzed geometrically above, this happens when the body's angular velocity is exactly aligned with its axis of maximal moment of inertia.

This happened to [[Explorer 1#Results|Explorer 1]], the first [[satellite]] launched by the [[United States]] in 1958. The elongated body of the spacecraft had been designed to spin about its long (least-[[inertia]]) axis but refused to do so, and instead started [[Precession|precessing]] due to energy [[dissipation]] from flexible structural elements. Later it was understood that on general grounds, the body ends up in the spin state that minimizes the [[Kinetic energy|kinetic]] [[rotational energy]] for a fixed angular momentum (this being the maximal-inertia axis).

== See also ==