Physics Section 7.1 Define and apply circular motion What is circular motion? Any object that revolves about a single point or axis undergoes circular motion. Tangential speed (v t ) is the speed of an object in circular motion. If the tangential speed is constant the motion is uniform circular motion.

Centripetal acceleration causes an object to change its direction. It is directed toward the center of the circular path. a c = (v t ) 2 a c = centripetal acceleration (m/s 2 ) r v t = tangential speed (m/s) r= radius of the circular path (m)

A rope attaches a tire to a tree limb. A girl swinging on the tire has a centripetal acceleration of 3.0 m/s 2. If the length of the rope is 2.1 m, what is the girl’s tangential speed? Tangential acceleration causes a change in the tangential speed of an object in circular motion. Centripetal Force is a force directed toward the center of object in circular motion. It causes centripetal acceleration. F c = m(v t ) 2 F c = centripetal force (N) r v t = tangential speed (m/s) r = radius (m)

example A pilot is flying a small airplane at 56.6 m/s in a circular path with a radius of m. The centripetal force needed to maintain the planes circular motion is 1.89 X 10 4 N. What is the planes mass?

Centripetal force acts at a right angle to the tangential velocity. If the centripetal force is removed, the object moves in a straight line in the direction of the tangential velocity.

Inertia will cause an object to move to the outside of a circle. It is sometimes referred to as centrifugal force. Assignment Page 239 Problems 1-3, 5-7