Transcript Universal Gravitation - Stony Brook University

Newton’s Law of
Universal Gravitation
Dan Li
SUNY-Stony Brook
12/09/2002
Outline
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Who Found It?
The Statement of the Law
Gravity Near the Earth’s Surface
Geophysical Applications
Satellites
Who Found It?
The Statement
of the Law

Magnitude: Every particle in the universe
attracts every other particle with a force that is
proportional to the product of their masses and
inversely proportional to the square of the
distance between them.
F G

m1m2
r2
G  6.67 1011 N  m2 / kg 2
Direction: This force acts along the line joining
the two particles.
Gravity Near the Earth’s Surface
m1m2
mE m

G
 mg
2
2
r
rE
m
g  G 2E
rE
grE2
mE 
 5.98 1024 kg
G
F G
Some Geophysics
Some Geophysics: Applications
Variation in g: Gravity Anomalies
To investigate
 the structure of the Earth’s crust
 mineral deposit
 oil exploration
Some examples
 mineral deposit
 oil exploration
Satellites
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What keeps a satellite up?
Its high speed
How they move?
2
msat mE
vsat
G 2 m
r
r
Moon:
Special Satellite
22
Mass
:
7.35

10
kg
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Dis tan ce :1.5 108 km

Period : 29.5306days
Earth: the Satellite of the sun
Summary
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a force “acting at a distance” even though
there is no contact
a useful tool to explore in space
Thank you!