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Rev. 1
REVIEW SHEET #10:
Gravitation
Newton’s Law of Gravitation:
Every particle of matter in the universe attracts every
other particle of matter with a force that is directly proportional to the product of the
masses of the particles and inversely proportional to the square of the distance
between them.
1
2
2
12
g
Gm m
F
r
=
the constant G=6.67x10
11
N*m
2
/kg
2
The direction of F
g
is along the straight line that joins the two masses.
If a mass m is subject to more than one gravitational force, the total gravitational force is
the vector sum of all the individual gravitational forces that act on m.
The weight of a body of mass m is the total gravitational force exerted on the body by all
other bodies in the universe.
For a body near the surface of the earth, the weight of the
body is considered to be just the gravitational force that the earth exerts on the body:
2
E
E
g
mg
Gm m
w F
R
=
=
=
Hence
2
E
E
Gm
g
R
=
(m
E
= earth’s mass = 5.98x10
24
kg;
R
E
= earth’s mean radius = 6.38x10
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This note was uploaded on 09/11/2011 for the course PHYS 0174 taught by Professor Kohler during the Spring '08 term at Pittsburgh.
 Spring '08
 KOHLER
 Physics, Force, Mass

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