1. "Calculate the radius of a planet with mean density of 3.0x10^3 m2kg-3, from which a golf ball can be thrown to infinity as a velocity of 40 ms-1" 2. Relevant equations I've been looking at the equation of: Vesc=sqroot of 2*G*M/r and rearranging to r=2*G*M/Vesc. However, the trouble is, I'm struggling to get the mass from the density? It appears I don't have enough information, or I'm barking up the wrong tree so to speak? 3. The attempt at a solution can anyone point me in the right direction please?