A skater has moment of inertia 5 kg·m² spinning at 4 rad/s. She pulls her arms in, reducing $I$ to 2 kg·m². Her new angular speed in rad/s is:

An ice skater rotating with arms extended pulls them in. Her moment of inertia decreases; her angular speed:

Angular momentum of a system is conserved when:

In pure rolling motion, the point of contact of the body with the surface has zero instantaneous velocity.

A solid cylinder rolls without slipping. The ratio of translational KE to the total KE is:

For pure rolling without slipping of a wheel of radius $R$: