1. Uniform Circular Motion

2. 4 https://www.youtube.com/watch?v=FVo2q dXxQ7o https://www.youtube.com/watch?v=FVo2q dXxQ7o

3. 4 https://www.youtube.com/watch?v=i1aXQn s4b6M ​ https://www.youtube.com/watch?v=i1aXQn s4b6M

4. 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.

5. 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

6. 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) 4 The acceleration of an object in uniform circular motion is always toward the center of the circle, called centripetal acceleration

7. 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

8. NASA 4 http://www.youtube.com/watch?v=bs2orRF uolk http://www.youtube.com/watch?v=bs2orRF uolk

9. 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 net = 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.

10. Mythbusters 4 http://app.discoveryeducation.com/player/vi ew/assetGuid/17BDD8FF-82B6-4655- 921E-D724B968360D http://app.discoveryeducation.com/player/vi ew/assetGuid/17BDD8FF-82B6-4655- 921E-D724B968360D 4 Slo Mo 4 https://www.youtube.com/watch?v=zs7x1H u29Wc https://www.youtube.com/watch?v=zs7x1H u29Wc

11. Let’s Practice 4 The ball at the end of the string 0.5 m long moves in a circle. The ball has a mass of 0.25 kg and makes 2 revolutions every second. 4 Find the period of the ball.

12. What is the tangential velocity of the ball?

13. What is the centripetal acceleration of the ball?

14. What is the centripetal force of the ball on the end of the string?