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In previous pods, we introduced the concept of angular momentum. Angular momentum is always conserved when their are no torques acting on some object. This principle can be used by athletes to control how quickly their body rotates. This quiz focuses on the most famous example of this technique: spinning figure skaters.
$$ L = I \omega $$
The conservation of angular momentum states that, when no external torques are acting on some object, the angular momentum \( L \) of that object remains constant.
The rotational inertia of a point mass is given by the formula \( I = m r^2 \). To find the rotational inertia of a person's arm, more complicated math is required. Nevertheless, the point mass formula contains the concept you need to understand: when mass is farther away form the axis of rotation, it contributes MORE to the rotational inertia than when it is close to the axis of rotation.
The following two articles show a spinning figure skaters. At some points, a figure skater moves her arms inward in order to spin faster, than moves them outward when they want to stop spinning.
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