1. Round and round… Circular Motion

2. Circular Speed & Velocity When objects move in a circular path, we will only consider those that have a constant speed. If speed is constant then is velocity constant? –NO, VELOCITY IS ALWAYS CHANGING v v v v

3. Circular Speed & Velocity Velocity changes because the direction changes as the objects goes around the circular path. VELOCITY IS ALWAYS TANGENTIAL TO THE CIRCULAR PATH

4. Centripetal Acceleration In order for velocity to change direction, the object must accelerate Radius Centripetal means: Center Seeking

5. The Center-Seeking Acceleration acac

6. Example #1 Calculate the centripetal acceleration of a toy ball swinging with a speed of 12 meters per second on the end of a 1.44 meter long string.

7. Example #2 Calculate the velocity of a car that experiences a centripetal acceleration of 6 meters per second 2 as it moves through a turn with a radius of 5 meters.

8. Centripetal Force Inertia causes objects to travel STRAIGHT Paths can be BENT by FORCES CENTRIPETAL FORCE bends an objects path into a CIRCLE -- pulling toward the CENTER v c, F c, and a c constantly CHANGE DIRECTION, but not MAGNITUDE

9. The Center-Seeking Force FcFc

10. Calculating F c Newtons 2 nd Law? F = ma

11. Example #3 Calculate the centripetal force on a 2000 kilogram airplane making a turn with a radius of 1000 meters if it is moving at 300 meters per second.

12. Example #4 How far from the center of a merry-go-round is a 500 kilogram horse that is traveling at 3 meters per second if it experiences a force of 3000 newtons?

13. THE GRAVITRON The doors to the Gravitron close and it starts to spin. You are pushed against the outside edge of the ride and pinned there, You must be experiencing centrifugal force throwing you outward from the ride! Right?

14. How is this possible? As the Gravitron starts to spin, friction between your body and the ride start you moving Once you are moving, your body wants to go STRAIGHT … but you cant… The WALLS push you back in toward the center of the ride! vcvc FcFc

15. SUMMARY Compare circular SPEED & VELOCITY How do objects change velocity in circles? –Is it constant? –Equation? Which force causes circular motion? –Is it constant? –Equation?