1. Uniform Circular Motion

2. What is uniform circular motion? 4 Movement of an object at constant speed around a circle with a fixed radius 4 Can the velocity be accelerated even though it has constant speed? 4 Yes, because the velocity may change due to direction. If direction changes and velocity changes then an object can accelerate.

3. New terms for UCM TermSymbolUnitsExample Radiusrm3 m Centripetal acceleration acac m/s 2 2.5 m/s 2 toward the center Tangential speed vTvT m/s3.6 m/s PeriodTs4.7 s Centripetal force FcFc N1.2 N toward the center

4. Describing Circular Motion 4 A lower case r represents the position of a vector (the radius of the circle) 4 The direction of the vector can change but not its length (length is proportional to magnitude, which is speed) 4 The acceleration of an object in uniform circular motion is always toward the center of the circle, called centripetal acceleration

5. Circular Motion Equations 4 Centripetal acceleration (a c )- acceleration of an object in uniform circular motion. a c = v T 2 /r 4 Tangential speed (v T )- speed at which an object travels in a circular path. v T = 2πr/T an object will travel the distance of the circumference of the circle, which is represented by C = 2πr Time required for one complete revolution around a circle is called a period –Symbol is T –Units are seconds

6. What about net force? 4 The force that causes centripetal acceleration is called centripetal force 4 For an object in UCM, what direction is the net force? 4 The same direction as the acceleration – toward the center 4 F c = ma c 4 If you stop the acceleration, what direction will the object move? 4 The movement of the object is in the direction of the velocity or tangent to the circle.