physics
posted by Taylor on .
A satellite is in a circular orbit around an unknown planet. The satellite has a speed of 1.55 104 m/s, and the radius of the orbit is 5.50 106 m. A second satellite also has a circular orbit around this same planet. The orbit of this second satellite has a radius of 8.70 106 m. What is the orbital speed of the second satellite?

You can do this with Kepler's law, or with mechanics.
With mechanics
FIrst satellite
gravity force=centripetal force.
GMm/5.5E6^2= mv^2/5.5E6
solve for GM
Next satellite, do the same thing, but you know GM, so solve for v