1. Circular Motion

2. Uniform Circular Motion Speed of object may be constant Velocity is constantly changing Direction of the velocity is tangent to the circle

3. Measuring linear speed Circumference = 2 π r = π d Period (T) T = time to make one revolution (s / rev) Velocity = circumference/period v = 2 π r / T

4. Reference: http://webpages.uah.edu/~wilderd/ce ntripetal.JPG Acceleration and Force Acceleration is directed toward center (This is called centripetal acceleration, and is abbreviated a c.) Therefore, the net force (F c = centripetal force) acts on the object towards the center.

5. Centripetal Acceleration and Force Trends: As v increases, a c (F c ) increases As v decreases, a c (F c ) decreases Directions: a c (F c ) are inward v is tangent to the circle FcFc acac v

6. Calculating Centripetal Acceleration and Force a centripetal = F centripetal = ma c = m T is the period of revolution (s/rev) v = 2 π r / T v2v2 r v2v2 r

7. The Myth of Centrifugal Force Centrifugal Force does not exist!!!!! No outward force is being applied. The forces are only inward. If the centrifugal force existed, then a released object would move directly away from the center of the circle. However, the object will move in a path tangent to the release point.

8. Sample Problem An athlete whirls a 8.00 kg hammer tied to the end of a 1.5 m chain in a horizontal circle. The hammer moves at a rate of 2.5 m/s. A) What is the centripetal acceleration of the hammer? B) What is the size of the centripetal force?

9. Torque A turning force is called a torque. Torques always produce rotation. Torque is calculated as the perpendicular force times the lever arm.  = F x d d is the distance from where the force is applied to the fulcrum.

10. Torque Problems If an object is still (not moving), then all of the torques will be balanced. The clockwise torques will equal the counter-clockwise torques.