# Gravitational Potential Energy

1. Oct 28, 2005

### Lemmy

Okay I understand somewhat of this topic of grav potential energy but i got stumped on this one question. I am to find the mass of a satellite orbiting earth with the given variables of (F)(units: kN) which is the force the sattelite attracts the earth, and given the gravitational potential energy (-U). You are also givin the gravitational constant (G), and the earth (m_e)

How could you find the mass (m) of the sattelite without a given radius in the equation U=-(G*m_e*m)/r ?

How would i rewrite this equation

any help would be great thanks
lemmy

Last edited: Oct 28, 2005
2. Oct 28, 2005

### Physics Monkey

Hi Lemmy,

You are correct that if you were given only gravitational potential energy (and the mass of the Earth and G) then you couldn't figure out m or r separately but only in the combination m/r. However, you have an extra piece of information: you know the force. Write out what the force is and see if you can find a way to solve for m and r using both F and U.