A spacecraft is in orbit around a planet. The radius of the orbit is 2.9 times the radius of the planet (which is R = 71519 km). The gravitational field at the surface of the planet is 25 N/kg. What is the period of the spacecraft's orbit?

Question

anonymous · Answer

$$T = \sqrt{\frac{ 4\Pi ^{2}r ^{3} }{ GM }}$$

anonymous · Answer

How do you do it if M is not given?

anonymous · Answer

can you use this formula
$$M = \frac{ ar ^{2} }{ G }$$

anonymous · Answer

and what would a be?

anonymous · Answer

a = accleration due to gravity

anonymous · Answer

I can't seem to get the right answer. help please!

anonymous · Answer

put a=25
and try to solve

anonymous · Answer

I think r might be tripping me up. The radius of the orbit is 2.9 times the radius of the planet (which is R = 71519 km). but gravitational field is given at the surface of the earth

anonymous · Answer

ok

anonymous · Answer

that didn't give me the right answer either