SATELLITE

 SATELLITE

The heavenly body which revolves around the sun is called Planet e.g. the earth, while the heavenly body which revolves round the planets is called Satellite.  Moon is a natural satellite of the earth.

• Orbital speed of a satellite is independent of its mass and depends upon the radius of orbit.

i.e.  Vo = √gR . The orbital speed of a satellite revolving near the surface of the earth is 7.9 km/s. . Time period of a satellite revolving near the surface of the earth is 1hrs 24 min(84 min). . Period  of revolution of a satellite depends upon the height of the satellite from the surface of the earth. . Everybody inside the satellite depends on a state  of weightlessness. . Period of revolution of a satellite is independent of its mass. .If a satellite revolves in equatorial plane in the direction of the earth's rotation i.e from West to East with a period of revolution equal to time period of rotation of the earth on its own axis i.e . 24 h, then the satelliet will appear stationary  relative to the earth.Such a satellite  called geo- stationary satellite. Such a satellite revolves around the earth at a height of 3600 km. .INSAT 2B and INSAT 2C are geo- stationary satellites of India . It is used to reflect TV signals and telecast TV programs from one part of the work to another. .Polar satellite revolves around the earth in polar orbit at a height of 800 km. Time period of the satellite is 84 min. These are used  for weather forecasting and mapping,etc. NOTE: The earth is on its axis from West to East. This rotation makes the sun and the stars appear to be moving across the sky from East to West. ENERGY OF SATELLITE A Satellite revolution around the earth has potential energy as well as kinetic energy. It has potential energy because it remains in the gravitational field of earth and kinetic energy because it is in motion.         E = GMem/2Re + (- GMem/Re)         E  =  -  GMe/2Re Where, m is the mass of a satellite.