Is there a difference between the two? The problem reads: A grindstone of radius 4.0m is initially spinning with an angular speed of 8 rad/s. The angular speed is then increased to 10 rad/s over the next 4 seconds. Assume that the angular acceleration is constant. What is the average angular spped of the grindstone? r= 4m Wo= 8 rad/s W= 10 rad/s to= 0s t = 4s avg angular velocity = delta theta / delta t = 10 - 8 / 4 - 0 = .5 rad/s Is this correct? I only see equations for velocity, not speed.