## 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**.

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###### What is circular motion?

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###### Linear motion review

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###### Position and displacement

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###### Tangential velocity

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###### Tangential acceleration

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###### Summary

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###### Problem 1: Displacement

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###### Problem 2: Tangential velocity

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###### Problem 3: Tangential acceleration

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###### Problem 4: Constant acceleration equation 1

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###### Problem 5: Constant acceleration equation 2

**Answers**

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**.

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