1. Notes 6.2: Circular Motion

2. Circular Motion – when a force causes an object to curve in a full circle.
There are 2 types of circular motion to be familiar with:
1. Rotation – an object spins around an internal axis.
Example: bike tire, figure skater
Earth rotates once on it’s axis in 24 hours

3. 2. Revolution – object moves around an external axis
Example: rider on a carousel
Earth revolves around the sun

4. We can describe circular speeds in 2 ways.
1. Angular speed – rate at which something turns (rpm)
A CD spins at 200 rpm

5. 2. Linear speed- distance traveled around the circle divided by time.
Units: m/s

6. Example: A CD takes 0. 3 seconds to make one revolution
Example: A CD takes 0.3 seconds to make one revolution. If the radius of the CD is 6 cm, how fast is a speck of dust on the outside of the CD moving?
Answer:
t = 0.3 sec v =(2πr)/t
r = 6cm = 0.06m v = (2 x 3.14 x .06)/0.3
v = ? v = 1.26 m/s

7. When an object is rolling, it has both linear and rotational motion.