The direction associated with rotational motion

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

a magnitude
a direction

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

Image taken from a video of Race Across America Ultra Cycling Highlights of 2019



  Q:  If a cyclist is riding East at 20 mph, then his velocity is ...
            what?

The velocity is 20 mph East. Simple. But in the rotational world, things aren't so obvious. Consider the spinning record in the video clip below (click the image to start the video).

Video of record spinning on turntable courtesy of AXZM



  Q:  Which direction is the record 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 object is spinning
Stick out your right thumb

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

Let's look at this picture again:

Image taken from a video of Race Across America Ultra Cycling Highlights of 2019



  Q:  If a cyclist is riding East at 20 mph, the ANGULAR velocity
            of his front wheel is in what direction?

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