Circular Motion
So far we've learned about the motion of objects that move left, right, up and down. 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 (an orbit is actually an ellipse, but we're going to start by treating it as a circle).
Technically, circular motion is 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 learn about uniform circular motion where an object continues traveling in a circle at a constant speed. This is a simpler version of circular motion so we can describe it using some new variables: period and frequency.
We'll cover rotational motion in the next lesson, and then we'll learn how to connect circular and rotational motion.
Circular motion will come up again when we learn about centripetal acceleration and force, which explain why an object moves in a circle.
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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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Circular motion recap
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Uniform circular motion
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Radius and circumference
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Period and frequency
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Velocity
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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
Multiple-Choice Questions
Answers
Free-Response Questions
Circular motion
So far we've learned about the motion of objects that move left, right, up and down. 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 (an orbit is actually an ellipse, but we're going to start by treating it as a circle).
Technically, circular motion is 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 learn about uniform circular motion where an object continues traveling in a circle at a constant speed. This is a simpler version of circular motion so we can describe it using some new variables: period and frequency.
We'll cover rotational motion in the next lesson, and then we'll learn how to connect circular and rotational motion.
Circular motion will come up again when we learn about centripetal acceleration and force, which explain why an object moves in a circle.
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