Tis ppt gives u a brief glance on the following topics: Escape Speed Earth Satellites Geostationary And Polar Satellites Weightlessness If u want to download the ppt mail me to raviteja711@gmail.com

2. Escape Speed
Earth Satellites
Geostationary And Polar Satellites
Weightlessness

3. ESCAPE SPEED
 Escape speed on earth (or any other planet) is defined as the
minimum speed with which the body has to be projected
vertically upwards from the surface of the earth(or any other
planet) so that it just crosses the gravitational field of
earth(or of that planet) and never returns on its own.
 For a spherically-symmetric body, escape velocity is
calculated by the formula :
 Where G is the universal gravitational constant
G=6.67×10−11 m3 kg−1 s−2 . M the mass of the planet, star or
other body, and r the distance from the center of gravity

4. Important points :
 The value of escape speed does not
depend on the mass (m) of the body
and its angle of projection from the
surface of earth or a planet.
 It depends on the radius of the planet
from the surface of which the body is
projected.
 If a body is projected from a planet
with a speed v which is smaller than
the escape speed ve (i.e., v < ve), the
body will reach a certain height and
may either move in an orbit around
the planet or may fall back to the
planet .
 The escape velocity from the surface
of the Earth is about 11.2 km/s or
25,055 miles per hour.

5. Problems With Equation Near Earth
 The calculated escape velocity from gravity near the Earth's surface of
11.2 km/s or 26,000 miles per hour is too high to be practical. Also, the
effect of the Sun is not taken into account.
Assumes extremely high acceleration :
 A major problem with the escape velocity from gravity value is that the
velocity is calculated at or near the Earth's surface. An infinite
acceleration would be required to project an object at 11.2 km/s from the
Earth's surface. Also, it would be very difficult—if not impossible—for a
rocket to attain a velocity of 11.2 km/s relatively close to the Earth's
surface. The Saturn rocket that was used to go to the Moon did not reach
that speed until it was over 193 km (180 miles) from the Earth's surface.
Rocket would burn up
 Also, in order to reach the escape velocity at lower altitudes, the rocket
would be traveling at hypersonic speed, which would be so far above the
speed of sound that it could cause the burn-up of a rocket exterior
before it left the Earth's atmosphere. Realistically, a rocket would have to
build up its speed until it reached the extreme upper atmosphere, where
air resistance is negligible at high speeds.

6. Earth Satellites
 Earth satellites are the objects which revolve around the earth.
 Their orbits around the earth are circular or elliptic.
 Moon is the only natural satellite of the earth with a near
circular orbit with a time period of approximately 27.3 days
which is roughly equal to the rotational period of the moon
about its own axis.
 With the advancements of science and technology, since 1957,
many man made satellites have been put in different orbits
around the earth.
 Russians were the first to launch the artificial satellite Sputnik
I, on Oct 4, 1957. India launched its first artificial
satellite,Aryabhatta in 1957. Since the Indi has put many
satellites in various orbits around the earth e.g., Bhaskara,
Rohini, Apple, IA, IB, Insat, IRS etc.

8. Orbital Speed :
 Orbital speed of a satellite is the minimum speed required
to put the satellite into a given orbit around earth.
 Expression - v = sqrt(Re.g) Where, g=9.8 m/s & Re = radius
o
of earth. The value for orbital velocity was found to be 7.9
km/s.
 It is independent of mass of the satellite.
 Decrease with an increase in the radius in the radius in the
height of satellite.
 Depends upon the mass and radius of the earth/planet around
which the revolution of satellite is talking place.
 The direction of orbital speed of a satellite at an instant is
along the tangent to the orbital path of satellite at that instant.

10. Time Period And Height Of A Satellite
 Time period of a satellite is the time taken by satellite to
complete one revolution around the earth and is denoted by
T.
 By substituting the values we get, T = 84.6 minutes.
 It means that a satellite orbiting close to the surface of the
earth has a time period of revolution about 84.6 minutes.
 The height of a satellite is given by the exp.
 By substituting the values, h=36000m

11. Geostationary And Polar Satellites:
 A satellite whose period of
revolution is 24 hours, is a
geostationary satellite.
 It always appears to be at a fixed
point in space, because the period of
rotation of the Earth about its own
axis is also equal to 24 hours.
 Knowing T = 24 hours, g = 9.8 ms-1,
the height of a geostationary satellite
is calculated to be 36000km.Its
orbital velocity is 3.1 km/s.
 Its plane of orbit is the equatorial
plane.
 It revolves from west to east which is
similar to the Earth's movement.
 It is very useful in
telecommunication.

12.  Polar orbiting weather satellites
circle the Earth at a typical altitude
of 850 km (530 miles) in a north to
south (or vice versa) path, passing
over the poles in their continuous
flight. Polar satellites are in sun-
synchronous orbits, which means
they are able to observe any place on
Earth and will view every location
twice each day with the same general
lighting conditions due to the near-
constant local solar time. Polar
orbiting weather satellites offer a
much better resolution than their
geostationary counterparts due their
closeness to the Earth. Satellites in
polar orbits are used for
environmental and earth resources'
survey

13. Different types of satellites :
Astronomy satellites - Hubble Space Telescope
Atmospheric Studies satellites - Polar
Communications satellites - Anik E
Navigation satellites - Navstar
Reconaissance satellites - Kennan, Big Bird,
Lacrosse
Remote Sensing satellites - Radarsat
Search and Rescue satellites - Cospas-Sarsat
Space Exploration satellites - Galileo
Weather satellites - Meteosat

14. Weightlessness
 When the astronaut in the spaceship is orbiting the
Earth, then both, the astronaut and the spaceship are
in a state of free fall towards the Earth. During a free
fall, both travel downwards with the same
acceleration, equal to the acceleration due to gravity.
As a result, the astronaut does not exert any force on
the sides or floor of the spaceship, and the sides and
floor of the spaceship do not push the astronaut up.
The astronaut therefore experiences weightlessness
while orbiting around the Earth in a spaceship.