# Notes: A really fast Chapter 5 (Circular Motion) Important points

```Notes: A really fast Chapter 5 (Circular Motion)
Important points
1. An object moving in a circle of radius r with constant speed is said to be in uniform circular
motion. radial acceleration is equal to the velocity squared divided by the radius of the circle
2. A force is need to keep an object revolving in a circle and the direction of this force is toward the
center of the circle
3. Newton’s law of universal gravitation states that every object in the universe attracts every
other object with a force proportional to the product of their masses and inversely proportional
to the square of the distance between them
4. Keplar’s Laws
a. Keplar’s first law: The path of each planet around the sun is an ellipse with the sum at
one focus
b. 2nd law: each planet moves so that the planet sweeps out in equal areas in equal
periods of time
c. The ratio of the squares of the periods of any two planets is equal to the ratio of the
cubes of their mean distances from the sun p2 = d3
```