planet of mass m is moving in an elliptical orbit around the sun of mass M. maximum and minimum distance of the planet from the sun is r1 and r2. Find the angular momentum of planet about the sun.(Consider M to be fixed in it's position.) Angular momentum= m(R*v) At farthest point from sun angular momentum is mr2v2 and at the closest point it is mr1v1 I am thinking to make third equation with the forces of interaction between the two bodies bodies. that might be something like centrifugal force = gravitational force of interaction, but i don't know that value of instantaneous radius of curvature of the m at the two points. So this is my problem. what should i do?