help with astronomy!?

Question

Mars has two small satellites, Phobos and Deimos. Phobos circles Mars once every 0.31891 day at an av. altitude of 5980km above the planet's surface. The diameter of Mars is 6794km. Using this information, calculate the mass and average density of Mars.

please use simple wording, i cant understand the question. i feel so in over my head. WHY DID I PICK THIS AS MY MAJOR!?

thanks so much for your help.

Answer 1

using the time and the radius of the satellite phobos calculate the centrifugal force exerted on phobos. that is equal to the gravitational force between mars and phobos. using that u should be able to calculate the mass and density of mars