The Spinning Skater

Angular Momentum

Angular Momentum ($L$) is the rotational equivalent of linear momentum and is conserved in a closed system. It is the product of an object's Moment of Inertia ($I$) and its Angular Velocity ($\omega$). The formula is $L = I\omega$.

The "Ice Skater" Effect

• Moment of Inertia ($I$) measures how hard it is to spin something. It's lower when mass is closer to the center.
• When the skater pulls their arms in, their $I$ decreases.
• Because Angular Momentum ($L$) must stay the same, their Angular Velocity ($\omega$) must increase to compensate. Result: they spin much faster!