Lecture 25
Friday 10/23/09
Chapter 12:
Gravitation
Newton’s Universal Law of Gravitation
•
Gravitational forces are always
attractive
•
The magnitude of the gravitational force between two point
particles is
• The
gravitational field
at each point in space is the
weight of a point mass at that point divided by that mass
• The
gravitational potential energy
is
• The
escape speed
is
±
g
U
=
±
Gm
1
m
2
/
r
F
=
Gm
1
m
2
/
r
2
v
escape
=
2
GM
/
R

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Newton
:
The moon orbiting the earth is actually falling towards
the earth
like an apple falling from a tree (Newton’s
apple), but it just keeps missing hitting the earth