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Fundamentals

The angular velocity refers rate at which an point rotates about the axis of rotation. It is typically expressed in radians/second, revolutions/minute (rpm), or degrees/second. The angular velocity can be related to the linear velocity and the distance the point is from the axis of rotation. See How to Think About This Situation for more details.

 

There are four similar versions of this question. Here is one of the versions:

Version 1:
A flywheel having a radius of 20 cm has a spin rate of 12 revolutions per second. Which expression must be used to determine the angular velocity of the flywheel in radians per second?
12 • 2 • π • 20
12 • 2 • π • 20 / 100
12 • 20
12 • 2 • π
12 • 20 / 2 / π

 

How to Think About This Situation

Angular velocity is the rate at which a point on the flywheel rotates about its axis. This rate is measured as a change in the angular position divided by a change in time, Δθ/Δt. Angular position change can be measured in a variety of units. The standard unit is the radian. Angular position change can also be measured in degrees. A 360-degree change in angular position is equivalent to 2•π radians. Angular position change can even be measured in terms of the number of revolutions where a single revolution is equivalent to a change in angular position of 2•π radians.  That's the case in this question - you're told the time (1 second) and the number of revolutions. So if you multiply the number of revolutions by 2•π radians/revolution, you will have the angular position change in radians. Dividing that by the time (1 second) yields the angular velocity in radians per second. 

 

Try these links to The Physics Classroom Tutorial for more help with understanding the concept of angular position and displacement:

​Sorry. We hope to add resources in the future.
 


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