3.3.1—Angular speed

Angular speed ω measures the angle swept per unit time, in radians per second. For a particle at radius r, its tangential speed is v=rω, so equal angular speed does not mean equal linear speed at different radii.

Use radians, not degrees, in v=rω and in arc-length relations. Keep the direction of v tangent to the circle even though ω describes the rotation about the centre.

At ω=4 rad s⁻¹, a point 0.25 m from the axis moves at v=1.0 m s⁻¹; a point twice as far moves twice as fast.

Angular speed is not the same as revolutions per second: f revolutions per second gives ω=2πf.