Man-made Satellites

3.3  Man-made Satellites
  • If the linear speed of satellite, v is less than required speed, staellite will fall to a lower orbit
  • Satellite will revolve towards Earth until it enters atmosphere
  • High speed movement against air resistance will produce heat, satellite burns
Geostationary satellite Non-geostationary satellite
Orbits the Earth
\(T=\sqrt{\dfrac{4\pi^2 r^3}{GM}}\)
Direction of motion same as the direction of Earth rotation Direction of motion doesn't have to be the same as the direction of Earth rotation
T = 24 hours T can be longer or shorter than 24 hours
Above the same geographical location Above different geographical location
Function: communication satellite Function: Earth imaging, GPS, weather forecast
Example: MEASAT Example: TiungSAT, RazakSAT, Pipit, ISS
  Escape velocity  

The minimum velocity needed by an object on the surface of the Earth to overcome gravitational force and escape to outer space.

Earth's escape velocity: \(11\,200\,ms^{-1} /\;40\,300\,kmh^{-1}\)

  Escape velocity formula  

Benefits and implications of Escape Velocity

  1. Earth is able to maintain a layer of atmosphere around it
    • Molecules in atmosphere has velocity (\(500\,ms^{-1}\)) lower than Earth's escape velocity
    • unable to escape to outer space
  2. Planets and jets won't escape to outer space
    • both have speeds lower than Earth's escape velocity
  3. Rockets need to be launched into outer space
    • uses a lot of fuels to produce large thrust
    • produce high velocity that is larger than Earth's escape velocity