Suppose you had two bars with mass m and length L and there were parallel to each other, along the same line and a distance d apart. How do we calculate the force between them? ______________ ______________ |-----L--------| |------d-------| |-------L-------| I figured out how to do it if it is a bar and point mass. Then I thought maybe if add up the particles forces along the line but I couldn't get it to work out. Density = E = M/L; dm = E dr F = G(massofparticle)E dr/r^2 = G(mass of particle)(1/r) mass of partlcle = dm = E dr And then evaluate the integral again to get the force for the sum of particles but I don't think that method works.