3. Submitted To :
Mrs. Linimol.k.s
Faculty in physical science department
Sreenarayana training college poochakkal
Submitted By :
Renju.R
Option : Physical Science
Register Number : 18214383018
Submitted On : 7.9.2015
6. Newton’s Law of Universal Gravitation
states that gravity is an attractive
force acting between all pairs of
massive objects.
Gravity depends on:
Masses of the two objects
Distance between the objects
Universal Gravitation
9. Bottom Line
• Gravity is reduced as the inverse square
of its distance from its source increased
• Fg ~ 1/r2
•
Gravity’s Inverse Square Law
r 2r 3r 4r 5r 6r 60r
Fg Fg Fg Fg Fg Fg Fg
1 4 9 16 25 36 3600
10. Bottom LineGravity’s Inverse Square Law
Gravity decreases with altitude, since
greater altitude means greater distance
from the Earth's centre
If all other things being equal, on the top of
Mount Everest (8,850 metres), weight
decreases about 0.28%
11. Bottom LineGravity’s Inverse Square Law
Astronauts in orbit are NOT weightless
At an altitude of 400 km, a typical orbit of
the Space Shuttle, gravity is still nearly
90% as strong as at the Earth's surface
12. Bottom LineLaw of Universal Gravitation
Newton’s discovery
Newton didn’t discover gravity. In stead, he
discovered that the gravity is universal
Everything pulls everything in a beautifully
simple way that involves only mass and
distance
13. Bottom LineLaw of Universal Gravitation
Universal gravitation formula
Fg = G m1 m2 / d2
Fg: gravitational force between objects
G: universal gravitational constant
m1: mass of one object
m2: mass of the other object
d: distance between their centers of mass
15. Bottom LineLaw of Universal Gravitation
Fg = G m1 m2 / d2
Gravity is always there
Though the gravity decreases rapidly with
the distance, it never drop to zero
The gravitational influence of every object,
however small or far, is exerted through all
space
16. Bottom LineLaw of Universal Gravitation Example
Mass 1 Mass 2 Distance Relative Force
m1 m2 d F
2m1 m2 d
m1 3m2 d
2m1 3m2 d
m1 m2 2d
m1 m2 3d
2m1 2m2 2d
17. Law of Universal Gravitation Example
Mass 1 Mass 2 Distance Relative Force
m1 m2 D F
2m1 m2 d 2F
m1 3m2 d 3F
2m1 3m2 d 6F
m1 m2 2d F/4
m1 m2 3d F/9
2m1 2m2 2d F
18. Universal Gravitational Constant
The Universal Gravitational Constant (G)
was first measured by Henry Cavendish
150 years after Newton’s discovery of
universal gravitation
20. Universal Gravitational Constant
Cavendish’s experiment
Use Torsion balance (Metal thread, 6-foot
wooden rod and 2” diameter lead sphere)
Two 12”, 350 lb lead spheres
The reason why Cavendish measuring the G
is to “Weight the Earth”
The measurement is accurate to 1% and his
data was lasting for a century
24. Isaac Newton’s Influence
People could uncover the workings of the physical
universe
Moons, planets, stars, and galaxies have such a
beautifully simple rule to govern them
Phenomena of the world might also be described by
equally simple and universal laws
Editor's Notes
Figure 5-1 If the sphere’s radius is doubled, the sphere’s surface increases by a factor of 4.
Figure 5-1 If the sphere’s radius is doubled, the sphere’s surface increases by a factor of 4.
p. 83: The attraction between these spheroidal friends depends on the distance between their centers.
Figure 5-1 If the sphere’s radius is doubled, the sphere’s surface increases by a factor of 4.
Figure 5-1 If the sphere’s radius is doubled, the sphere’s surface increases by a factor of 4.
Figure 5-1 If the sphere’s radius is doubled, the sphere’s surface increases by a factor of 4.
