According to the Law of Conservation of Angular Momentum, if the net external torque is zero: $L_{initial}=L_{final}⟹I_1{\omega }_1=I_2{\omega }_2$ Given:

• $I_2=\frac{1}{2}{I}_1$ Substituting: $I_1{\omega }_1=(\frac{1}{2}{I}_1){\omega }_2$ ${\omega }_2=2{\omega }_1$ The angular speed doubles. This explains why skaters spin much faster when they pull their limbs toward their axis of rotation.