1. The problem statement, all variables and given/known data An imaginary planet has a diameter twice that of our earth. The planet has one moon with an orbital radius of 5.0x10^7 km and orbital period of 10 earth days. Determine the strength of the gravitational field at the surface of the planet. Radius of earth = 6.38 x 10^6m Orbital radius of moon = 5x10^10m orbital period = 8.64 x 10^5 s 2. Relevant equations r^3/T^2 = GM/4pi^2 g = GM/r^2 i think that's all..?... 3. The attempt at a solution GM = (4pi^2(5x10^10)^3)/(8.64x10^5)^2 = 6.61 x 10^21 g = 6.61x10^21/(12.76x10^6)^2 = 40597576.67N/kg this number is massive!!! I must be doing something wrong. any help?