Gravitation has been the most common phenomenon in our lives but somewhere down the line we don't know musch about it. So here is a presentation whic will help you out to know what it is !! I'll be makin it available for download once i submit it in school :P :P ! Coz last one of the brats showed the same presentation that i uploade and unfortunatele his roll number fell before mine ! I was damned..:D :D :P

1. GRAVITATION
Gravity is matter's
memory it once was
light.

2. • Gravitation, the attractive force existing
between any two particles of matter.
• It was Sir Isaac Newton who not only provided
this explanation in his famous inverse square
law of gravitation, but managed to "synthesize"
the explanation of motion on earth and motion in
the heavens. This had profound philosophical
and scientific consequences.
What Gravitation is??

3. • The unification into what became the laws of
gravitation became a symbol of the predictive
and quantitative power of science. The fact that
a single law could explain the motion of a
cannonball and the motion of Mars
revolutionized our understanding of our place in
the universe.

4. • Kepler’s First Law (Law of Orbits): Each
planet moves in an elliptical orbit with the Sun at
one focus.
KEPLER’S LAWS

5. • Kepler’s Second Law (Law of Areas): The
speed of planet varies in such a way that the
radius vector drawn from the

6. • Sun to a planet sweeps out equal areas in equal
times. Thus the law states that the areal velocity of
the planet is constant.
• Areas; A1, A2 and A3 are swept by the radius vector
in equal times. So, according to Kepler’s second
law,
A1 = A2 = A3

7. • Also, the planet covers unequal distances S1, S2
and S3 in equal times due to the variable speed of
the planet. Maximum distance is covered in a given
time when planet is closest to the Sun. When the
planet is closest from the sun, its velocity and the
kinetic energy of the planet is maximum.

8. • When the planet is farthest from the Sun, its velocity
and the kinetic energy is minimum. However, the
total energy of the planet remains constant.

9. • Kepler’s Third Law (Law of Periods)- The square
of the period of revolution of a planet around the
Sun is proportional to the cube of the semi-major
axis of its elliptical orbit. AB is the major axis and CD
is the minor axis. AO or OB is called semi-major
axis.
• Let, T = Period of revolution of planet around Sun.
R = length of semi- major axis
According to Kepler’s third law,
T2 ∝ R3 or T2 = KR3

10. • Let T1 and T2 be the periods of any two planets
around the Sun.
Let , R1 and R2 be the lengths of their
respective semi – major axes
Then,

11. • Every particle of matter in the universe attracts
every other particle with a
• force which is directly proportional to the product
of their masses and
• inversely proportional to the square of the
distance between them.
UNIVERSAL LAW OF
GRAVITATION

13. • The force of attraction between any two particles
in the universe is known as force of gravitation.
• The force of gravitational attraction between the
two bodies acts along the line joining their
center. This force is mutual and
Characteristics of
gravitational force

14. • Combining these factors we get 
&
• {Where the value of G in SI units is (6.67 × 10–
11 Nm2 kg–2). The universal gravitational
constant (G) is numerically equal to the force of
attraction between two bodies, each of unit
mass, separated by unit distance.

15. • In vector notation, Newton’s law of
gravitation is written as follows:

16. • Let us consider a body of mass
m lying on the surface of the
Earth of mass M and radius R.
Let g be the value of
acceleration due to gravity on
the free surface of Earth.
ACCELERATION DUE TO
GRAVITY OF THE EARTH

17. •
• Since the value of g at a given
place on the Earth is constant
and R is also constant
Therefore 
• Thus, the value of acceleration
due to gravity decreases with
increase in height above the
surface of Earth.
Variation of g with Altitude
(Height)

18. • We know that,
• ∴
Loss of Weight at Height h(<<R)

19. • Assume the Earth to be a
homogeneous sphere (having
uniform density) of radius R
and mass M. If at a depth h,
the gravity will be gh. Then,
the difference is given by 
Variation of g with Depth

20. • Here g- gh gives the decrease in the value of
g.
• Since g is constant at a given place of the
Earth and R is also a constant,
∴

21. Thus the value of acceleration
due to gravity decreases with
the increase of depth.

22. • The force of gravity is a
conservative force and we can
calculate the potential energy
of a body arising out of this
force, called the gravitational
potential energy.
GRAVITATIONAL POTENTIAL
ENERGY

23. • This work done is equal to the gravitational
potential energy U of mass m.

24. • According to convention, the
gravitational potential energy at
the surface of the Earth is taken
to be zero.
∴ U = m x g
x h

25. • A satellite is a body which is
continuously revolving around a
bigger body. Satellite may be
regarded as a ‘secondary body’.
• The centripetal force required
by a satellite to move in a
circular orbit is provided by
the gravitational force of
attraction between the
satellite and the body around
which it revolves.
SATELLITES

26. • Planets can be said to be the
natural satellites of the sun.
• Moon is a natural satellite of
the Earth which revolves around
the Earth in a nearly circular
orbit of radius
• 3.85 x 105 km and completes one
revolution is 27.3 days.

27. • GEOSTATIONARY SATELLITES
• POLAR SATELLITES
TYPES OF SATELLITES

28. • A geosynchronous satellite is
a satellite in
geosynchronous orbit, with an
orbital period the same as the
Earth's rotation period. Such a
satellite returns to the same
position in the sky after each
sidereal day.
GEOSTATIONARY SATELLITES

29. • These satellites have
revolutionized
global communications, television
broadcasting and weather
forecasting, and have a number of
important defense and intelligence
applications.
USES

30. • Polar satellite is a satellite
that revolves around the Earth
in a polar orbit. It is usually
as close as ≈ 250km.
• As the Earth rotates about its
axis a polar satellite passes
many different places during
its motion unlike the
geostationary satellite.
POLAR SATELLITES

31. • Polar satellites are being used to record the
land and sea temperatures, take pictures of
cloud and predict the movement of winds and
ultimately forecast the weather reporting.
• It is hence also called a Monitoring or
weather satellite.
USES