ELLIPTIC ORBIT WITH NONCENTRAL FORCE-FIELD IN CELESTIAL MECHANICS

Equations describing planar motion along a constant elliptical orbit i n non-central force field are derived in a simple way and discussed. T he angular moment along the elliptical orbit is not a constant of moti on. The problem appears to be related to the problem of planar motion with drag force. Relations with related works are discussed. in presen ce of drag force, conditions for the force field to be derived from th e gradient of a function are discussed, and relation of this function with the potential function is indicated.