1. Rotational Motion
Chapter 8

2. 8.1 Describing Rotational Motion
Objects such as a Farris wheel, CDs, wheels, hands on a clock are all in rotational motion.
It is important to know the angular velocity and displacement and not just the linear velocity and displacement.

3. Radian Radian is used as the unit for angular motion
2 radians (rads) is equal to one revolution or 360o

4. Angular Displacement
The Greek letter theta, , is used to represent angular displacement.
The counterclockwise rotation is positive and the clockwise rotation is negative.
The units are rads.

5. Angular Velocity The speed of rotation is called the angular velocity.
The angular velocity is equal to the angular displacement divided by the time to make the rotation.
Angular velocity is represented by the Greed letter omega, .
The units are rads/s

6. Angular Velocity of the Earth

7. Linear Velocity of the Earth

8. Rigid Bodies Earth is an example of a rigid body.
Even if different points rotate different distances in each revolution
All points rotate through the same angle
All parts of a rigid body rotate at the same rate.
The Sun is not a rigid body, parts rotate at different rates.
Objects that we consider are rigid bodies.

9. Angular Acceleration
The change in angular velocity divided by the time to make the change.
Angular acceleration is represented by the Greek letter alpha, .
The units are rads/s2

10. Angular Frequency
The number of complete revolutions made by a rotating object in one second