# physics

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Physics Gravitation help...?

hello People

i need some help with my physics revision sheet. i cant 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...

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 å T^2
where R is the radius of the orbit and T is the time period 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.