What is the "direction" associated with a spinning object?

In the linear world, position, velocity, and acceleration are all vectors: each quantity has both

In the linear world, these directions are self-evident.



  Q:  If a car is driving North at 20 mph, then its velocity is ...
            what?

The velocity is 20 mph North. Simple.

But in the rotational world, things aren't so obvious. Consider the bicycle wheel in the video clip below (click the image to start the video).

Image and video courtesy of Adrian Choi



  Q:  Which direction is the wheel spinning?

The solution to this question is to use one version of the right-hand rule:

Raise your right hand
Curl your fingers partway toward your palm
Twist it around so that your fingers curl in the same direction that the wheel is spinning
Stick out your right thumb

Your right thumb now points in the "direction" of the spinning wheel.

Let's practice this idea with one of the bicycle wheels in the classroom ...