What is his angular speed, in revolutions per hour?

Question

A rider in a road bike race had an average linear speed of 39.253 km/hr. The Wheel of his bicycle had a diameter of 66cm. 

Answer 1

Angular speed is equal to linear velocity divided by the radius.

Since the diameter is 66 cm, the radius is 33 cm or .33 m.

Linear speed should be converted to meters from kilometers, so linear speed is 39253 m/h (multiply by 1000 to go from kilometers to meters.

Dividing the linear velocity be the radius, (39253 m/h )/ (.33 m) = 118948 radians/ hour.

Finally, there are 2 *pi radians per revolution, so we must divide the angular speed by 2 * pi.

(118948 radians/ hour)/ (2 *pi) = 18931 revolutions per hour.