hello People

I need some help with my physics revision sheet. I can't seem to get my head round it. If anyone could help by telling me how to work it out to get the right answer I would be grateful...

answers would also be appreciated.

OK here is the question:

mass of the earth = 5.97 * 10^24 kg
Polar Radius of Earth = 6.36 * 10^6 m

1) calculate the net force on a 1.08 * 10^3 Kg Satellite when it is in a polar orbit 2.02 * 10^7 m above the earths orbit...

2)show that the only stable orbit for the satellite orbiting at an altitude of 2.02 * 10^7 m has a period of appoximatly 12 hours.

3) for any object orbting around a primary body R^3 ∝ T^2
where R is the radius of the orbit and T is the time for the orbit.

show that thi is true and in doing so:
- state the conditions required for a stable orbit
- show that the conditions do not depend on the mass of the orbiting object.

4) discuss the particular requirements for an orbit that will keep the a satellite vertically above a certain point on earths surface.