1. The problem statement, all variables and given/known data Find the force exerted on a particle on the earth by the sun. 2. Relevant equations F = - GMm/r2 r = distance between sun and particle M = mass of sun G = Gravitational constant m = ? 3. The attempt at a solution Should I be using the other mass as that of the earth, or that of a pebble? I think it is the pebble. I mean it's the force BY the sun ON the pebble, but I want to make sure.