1. Rotational Motion and the Law of Gravity Causes of Circular Motion

2. Force That Maintains Circular Motion  Objects that travel in circular paths have forces that maintain that circular motion –Called Force that maintains circular motion (F c ) –Measured in Newtons (N) –Must be directed toward the center of the circular path

3. Force That Maintains Circular Motion  Force that maintains circular motion = mass * centripetal acceleration –F c =ma c  Force that maintains circular motion = mass * (tangential speed) 2 /radius –F c =mv t 2 /r  Force that maintains circular motion = mass * radius * (angular speed) 2 –F c =mrω 2

4. Describing the Motion of a Rotating System IIIInertia is often misinterpreted as a force –C–C–C–Centrifugal force NNNNot a force IIIIn order to maintain circular motion, the force that maintains circular motion must overcome inertia

5. Newton’s Law of Universal Gravitation GGGGravitational force – the mutual force of attraction between particles of matter EEEEvery pair of objects experience gravitational attraction between them MMMMost objects do not notice this attraction –O–O–O–Objects’ masses are too small and the distance between them is too large –G–G–G–Gravity is only noticeable over short distances when one object is very large (planet or moon-sized) –W–W–W–When both objects are very large, the gravity is noticeable at larger distances (sun and planets gravitational attraction keeps the planets in orbit)

6.  Gravitational force = constant * (mass 1 * mass 2)/(distance between center of masses) 2  F g =Gm 1 m 2 /r 2  G=6.673*10 -11 Nm 2 /kg2  Gravitational force is concentrated at the center of a spherical mass