1. Happy Thursday 11-12-16 Grab your calculator Get ready to take notes Get ready for your warm up No quiz tomorrow Next test: after Thanksgiving break

2. Warm up: Jeffrey pulls to the right on an 18 kg box with a force of 15 N while Eugene pulls to the left with a force of 22 N. A. What is F NET ? B. What is the acceleration of the box? C. Calculate the friction force if  =.15

3. 3 Uniform Circular Motion http://www.physicsclassroom.com/mmedia/circmot/circmotTOC.html

4. Question: Which moves faster on a merry-go-round: a horse on the inside or a horse near the outer rail? The horse on the outside It must move faster than the horse on the inside in order to make one full rotation

5. Uniform Circular Motion motion of an object in a circle with a constant or uniform speed

6. Velocity of circular motion When an object spins in a circle, the distance it travels is = to the circumference o the circle, or The time it takes for one full revolution of the circle = Period formula for the speed of a circle:

7. Centripetal Acceleration Centripetal Acceleration (a c ) toward the center of the circle,Centripetal Acceleration (a c ) acceleration is toward the center of the circle, Acceleration = change in speed OR directionAcceleration = change in speed OR direction Since an object moving in a circle is constantly changing direction, it is constantly accelerating!Since an object moving in a circle is constantly changing direction, it is constantly accelerating!

8. Centripetal Acceleration Formula a c = centripetal acceleration V 2 = velocity squared r= radius

9. Centripetal Acceleration practice problems: A car turns a curve at a speed of 20 m/s. If the radius of curvature of the turn is 100 m, what is the centripetal acceleration of the car? 4 m/s 2 A ball on a string swings in a horizontal circle of radius 2.0 m. If the speed of the ball is 15 m/s, what is the centripetal acceleration? 112.5 m/s 2

10. Centripetal force examples Gravitron gravitron 2 how to create artificial gravity Centripetal force examples Demos spinning tube trick

11. Centripetal Force Centripetal Force – A force that causes an object to move in a circle. Centripetal Force – A force that causes an object to move in a circle. Centripetal force points toward the CENTER of the circle. Centripetal force points toward the CENTER of the circle.

12. 12 Applying Newton’s 2 nd Law: Centripetal Force Always points toward center of circle. (Always changing direction!)

13. 13 Direction of Centripetal Force, Acceleration and Velocity Without a centripetal force, an object in motion continues along a straight-line path.

14. 14 Direction of Centripetal Force, Acceleration and Velocity

15. 15 What if velocity decreases?

16. 16 What if mass decreases?

17. 17 What if radius decreases?

18. The diagram below shows the top view of a 65 kg student at point A on an amusement park ride. The ride spins the student in a horizontal circle of radius 2.5 meters, at a constant speed of 8.6 m/s. The floor is lowered and the student remains stuck against the wall without falling to the floor. a.12,000 Nc.220 N b.1900 Nd.30 N The magnitude of the centripetal force acting on the student at point A is approximately ___.