# More Gravitation

1. Apr 15, 2010

### ride4life

1. The problem statement, all variables and given/known data
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?

2. Relevant equations

3. The attempt at a solution
a) Kepler's Third Law?
b) Fatest Velocity?
c) No Idea :D

2. Apr 15, 2010

### tiny-tim

Hi ride4life!
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"

3. Apr 15, 2010

### 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