1. Chapter 13
Gravitation
In this chapter we will explore the following topics:
-Newton’s law of gravitation, which describes the attractive force between two point masses and its application to extended objects.
-The acceleration of gravity on the surface of the Earth, above it as well as below it Gravitational potential energy Satellites (orbital speed and escape velocity).

2. Newton’s Law of Gravitation
Newton showed that the force that holds the Moon in its orbit is the same force that makes an apple fall.
Newton concluded not only that Earth attracts both apple and the Moon but also that every body in the universe attracts every other body; this tendency of bodies to move toward each other is called gravitation.
Newton proposed a force law that we call Newton’s law of gravitation: Every particle attracts any other particle with a gravitational force of magnitude
Newton solved the apple–Earth problem by proving an important theorem called the shell theorem: A uniform spherical shell of matter attracts a particle that is outside the shell as if all the shell’s mass were concentrated at its center.