How to Calculate Angular Motion
Converting between different units of angular velocity is straightforward. For revolutions per minute (rpm), divide the number of revolutions by time in minutes. For radians per second rad/s, multiply revolutions by 2π and divide by seconds. For example, a sculpture making 21 revolutions in 4 minutes has an angular velocity of 5.25 rev/min or 0.55 rad/s.
Even planets follow these same principles! Jupiter completes one revolution in 9.93 hours, giving it an angular velocity of 1.7×10^-4 rad/s. Despite this seemingly small number, Jupiter's massive radius (69,000,000 m) means its "surface" moves at an incredible 12,144 m/s.
Angular acceleration measures how quickly rotation speed changes. Calculate it by dividing the change in angular velocity by time. If our sculpture slows from 0.55 rad/s to zero in 5.5 seconds, its angular acceleration is 0.1 rad/s².
Try This! Figure skaters demonstrate angular velocity principles when they spin. By pulling in their arms (reducing their effective radius), they spin faster due to conservation of angular momentum. The record for fastest rotation is 308 rpm or 32.25 rad/s!