An isolated star collapses so that its radius is half its original radius. Both its angular momentum and its rotational energy must be conserved

Question

Quizplus · Accepted Answer

While angular momentum must be conserved in the absence of external torques, the rotational energy will not necessarily be conserved because it depends on both the moment of inertia and the square of the angular velocity. When a star collapses, its moment of inertia decreases, leading to an increase in angular velocity due to conservation of angular momentum. However, the change in rotational energy depends on how these quantities change relative to each other, and it can increase, contrary to the implication of conservation in the statement.

An Isolated Star Collapses So That Its Radius Is Half