Notes 6.2: Circular Motion

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

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

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

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

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

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