So far we've learned about the motion of objects that move left and right, up and down, and anything in between. But what about things that move around in a circle? Think of a car driving around a circular race track, a person riding on a carousel or a Ferris wheel, the moon orbiting the Earth or the planets orbiting the sun (most orbits follow an ellipse, but we'll treat them as circles for now).

Technically, circular motion would be considered 2D motion. But in this lesson, we're going to describe how an object moves around the circumference of a circle. Instead of describing the x and y motion of the object, imagine we take the x axis and we wrap it around in a circle. The object can only move clockwise and counterclockwise, so we only need one number to describe its position along that path.

Once we understand how to describe position, we'll learn about displacement, tangential velocity and tangential acceleration. We call this the tangential description of motion because the object's instantaneous motion points in a direction that is tangent to the circular path.

We'll also touch on uniform circular motion where an object travels in a circle at a constant speed due to a centripetal acceleration. Centripetal force will be covered later in the course.

We'll learn about rotational motion in the next lesson. After that, we'll explain how circular and rotational motion are related and how to convert between them.

Multiple-Choice Questions

Answers

• Flipping Physics - Circular Motion

So far we've learned about the motion of objects that move left and right, up and down, and anything in between. But what about things that move around in a circle? Think of a car driving around a circular race track, a person riding on a carousel or a Ferris wheel, the moon orbiting the Earth or the planets orbiting the sun (most orbits follow an ellipse, but we'll treat them as circles for now).

Technically, circular motion would be considered 2D motion. But in this lesson, we're going to describe how an object moves around the circumference of a circle. Instead of describing the x and y motion of the object, imagine we take the x axis and we wrap it around in a circle. The object can only move clockwise and counterclockwise, so we only need one number to describe its position along that path.

Once we understand how to describe position, we'll learn about displacement, tangential velocity and tangential acceleration. We call this the tangential description of motion because the object's instantaneous motion points in a direction that is tangent to the circular path.

We'll also touch on uniform circular motion where an object travels in a circle at a constant speed due to a centripetal acceleration. Centripetal force will be covered later in the course.

We'll learn about rotational motion in the next lesson. After that, we'll explain how circular and rotational motion are related and how to convert between them.