# Motion in a Circle

Seng Kwang
H2 Physics
Free
• 6 lessons
• 1 quizzes
• 10 week duration
• ##### Angular displacement and velocity

Learn how to describe circular motion quantitatively. The kinematics of circular motion.

• ##### Centripetal force

Learn what causes circular motion. The dynamics of circular motion.

## Angular Displacement

Observe the relationship between angular displacement $\theta$ and the arc length $s$ travelled by an object moving along a circle. Vary the arc length by dragging any of the blue dots.

Vary the radius of the circle $r$ using the slider and observe any changes.

What happens when $\theta = 1$?

## Angular Velocity

In the following interactive, you can adjust the radii and angular velocities of two different objects in uniform circular motion to observe the effect on linear velocity.

If the angular velocities of the objects are different, will it be possible for them to share the same linear velocity?

## Summary

1. $s = r\theta$ where $s$ is arc length, $r$ is radius of the circle and $\theta$ is the angular displacement.
2. One radian is defined as the angle subtended at the centre of a circle by an arc equal in length to the radius of the circle.
3. Angular velocity $\omega$ is defined as the rate of change of angular displacement, i.e. $\omega = \dfrac{d\theta}{dt}$.