physics
posted by jessica on .
A satellite is in a circular orbit around an unknown planet. The satellite has a speed of 1.80 104 m/s, and the radius of the orbit is 5.45 106 m. A second satellite also has a circular orbit around this same planet. The orbit of this second satellite has a radius of 8.60 106 m. What is the orbital speed of the second satellite?

centripetal force = gravitational force
m V^2/R = GMm/R^2
m is the satellite mass, which cancels out. M is the planet mass. G is the universal gravity constant.
Note that R*V^2 = G M, which is the same for both satellites
Use that fact to answer your question.