1. Circular Motion

2. In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular path.
It can be uniform, with constant angular rate of rotation and constant speed, or non-uniform with a changing rate of rotation.

3. Circular Motion Consider a ball on a roulette wheel.
It moves along a circular path of radius r.
Other examples of circular motion are a satellite in an orbit or a ball on the end of a string.
Circular motion is an example of two-dimensional motion in a plane.
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4. Uniform Circular Motion
To begin the study of circular motion, consider a particle that moves at constant speed around a circle of radius r.
This is called uniform circular motion.
The time interval to complete one revolution is called the period, T.
The period T is related to the speed v:
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5. Uniform circular motion can be described as the motion of an object in a circle at a constant speed. As an object moves in a circle, it is constantly changing its direction.
At all instances, the object is moving tangent to the circle.

6. Example 4.9 A Rotating Crankshaft
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7. Angular Position 1 rev = 360 = 2 rad
Consider a particle at a distance r from the origin, at an angle  from the positive x axis.
The angle may be measured in degrees, revolutions (rev) or radians (rad), that are related by:
If the angle is measured in radians, then there is a simple relation between  and the arc length s that the particle travels along the edge of a circle of radius r:
1 rev = 360 = 2 rad
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