# Homework Help: Find mass of mars given period of moon orbit and radius of orbit

1. Oct 10, 2009

### buttermellow

1. The problem statement, all variables and given/known data

Given data: A moon of mars orbits with a period of 459 minutes. The radius of the moon's orbit is 9.4x10^6 m. What is the mass of mars?

2. Relevant equations

3. The attempt at a solution

The only relevant equation I could find was Fmars on moon= (G*m1*m2)/(r2)

I have the radius, but to solve I would need the mass of the moon and the gravitational force. Could I use F=mv2/r ? Or how about v= $$\sqrt{}GM/r$$ ?

2. Oct 10, 2009

### buttermellow

Alright, I actually figured it out myself.

v= $$\sqrt{}Gm/r$$ and v=$$\omega$$*r

so the mass of mars is 6.5*10^23 kg!