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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).
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
m1m2
F G 2 .
r
http://www.physicstoday.org/daily_edition/physics_updat
e/another_close_look_at_big_em_g_em?type=PTFAVE
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.