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 (Fc)
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
Fc=mac
Force that maintains circular motion = mass * (tangential speed)2/radius
Fc=mvt2/r
Force that maintains circular motion = mass * radius * (angular speed)2
Fc=mrω2

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

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

6. Newton’s Law of Universal Gravitation
Gravitational force = constant * (mass 1 * mass 2)/(distance between center of masses)2
Fg=Gm1m2/r2
G=6.673*10-11 Nm2/kg2
Gravitational force is concentrated at the center of a spherical mass