my professor gave us this problem on the homework assignment about Fluid. Planet X is a sphere made entirely of the mythical metal exoferrum, which has density 2810 kg/m3. What is the period of orbit for a satellite in circular orbit just above the surface of Planet X? (That's right: I did not give you the mass or the radius of the planet!) i have no ideal which equation i should use. I dont know how to start this kind of problem ,please help!