Examples of Conservation of Angular Momentum Consider a spinning skater. A popular skating move involves beginning a spin with one's arms extended, then moving the arms closer to the body. This motion results in an increase of the speed with which the skater rotates increases. We shall examine why this is the case using our conservation law. When the skater's arms are extended, the moment of inertia of the skater is greater than when the arms are close to the body, since some of the skater's mass decreases the radius of rotation. Because we can consider the skater an isolated system, with no net external torque acting, when the moment of inertia of the skater decreases, the angular velocity increases, according to the equation L = Iσ . Another popular example of the conservation of angular momentum is that of a person holding a spinning bicycle wheel on a rotating chair. The person then turns over the bicycle wheel, causing it to rotate in an opposite direction, as shown below. Figure %: In a) the person holds the spinning bicycle wheel, and the angular momentum of the
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