# Circular Motion

AQA A - Circular Motion

- Created by: Amy
- Created on: 03-01-13 13:01

First 233 words of the document:

PHY4A

Circular motion

Angles and angular velocities

Radians

Radians are more fundamental units of angle than degrees. The definition of a degree is arbitrary:

1/360th of a full circle turn. In radians an angle is defined by:

Angle (rad) = arc length / radius

Since the circumference of a circle is 2r, there are 2 radians in one full revolution.

2 radians = 360° = 1 revolution

Measuring angles in radians has the additional benefit that for small angles

Sin = tan = in radians

Uniform circular motion and angular velocity

Uniform circular motion is simply motion along a circular path at a constant speed. If the

period is T, speed v is given by:

V = 2r/t

Angular velocity is rate of change of angular displacement a measure of rate of rotation.

Angular velocity is usually denoted by the Greek letter . It's units are rad¯¹

To convert from a frequency f to angular velocity , simply multiply by 2:

= 2f

Angular velocity and linear speed v are related by the equation:

v=r

Centripetal acceleration and force

Nothing will follow a circular path unless it is forced to.

Centripetal force is the force required to keep a body in uniform circular motion

Centripetal force and acceleration are always directed towards the centre of the circular path.

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