I've been trying to derive the Roche Limit and have been succesful for the most part but out of curiousity i was wondering how the tidal force equation was derived to be: -2GMmr/d^3 ?? Also on a related note i always get the constant at the front of the Roche Limit equation to be the cube root of two when apparently i should be getting two times this = 2.52, How is this constant found? (i gather Roche gets 2.44 due to spheroid deformation). Can anyone help with either of these problems.