There is an analogy between rotational and linear physical quantities. What rotational quantities are analogous to distance and velocity?
The rotational angle (rotational quantity) is the amount of rotation and is analogous to distance (linear physical quantity).
We define rotational angle to be the ratio of the ar length to the radius of curvature.
=. The arc length is the distance traveled along a circular path as shown in the figure below. r is the radius of the curvature.
Angular velocity () is analogous to linear velocity . The linear velocity for an arc length in time is . Now, =, = r