Geostationary Satellite: Height, Equator, Uses

[ride4life]

Homework Statement

It is possible to put a satellite into an orbit so that it stays in a fixed position over a point on the Earth's equator (a geostationary or geosynchronous satellite).
a) What would the be height of such a satellite above the Earth's surface?
b) Why must such a satellite orbit above the equator?
c) What are the uses of such a satellite, as compared to lower orbit satellites?

Homework Equations

The Attempt at a Solution

a) Kepler's Third Law?
b) Fatest Velocity?
c) No Idea :D

 

[tiny-tim]

Hi ride4life!

a) What would the be height of such a satellite above the Earth's surface?
b) Why must such a satellite orbit above the equator?
c) What are the uses of such a satellite, as compared to lower orbit satellites?
…
a) Kepler's Third Law?
b) Fatest Velocity?
c) No Idea :D

Forget Kepler (this is the second time, isn't it?) … there's hardly any exam questions on Kepler …

a) use Newton's second law and Newton's law of gravitation (remember, you want T = 24*3600)

b) what shape would the orbit be if it wasn't on the equator?

c) google or wiki for "geostationary"

 

[ride4life]

a) i used kepler's third law with
r=h+6.4x10⁶, with h being the distance from the Earth's surface to the satellite
and
T=86400s
ended getting 3.59x10⁸m
b) orbit above the equator would be a circle, elsewhere it would be an ellipse?
c) geostationary satellites move at the same speed as the earth, allowing transmitters to maintain links for periods of time, such as radio