Gravity.

the individual gravitational potential of each body at theposition of the other body can be expressed as follows v1 ( r2 ) = − gm1r [ er12 + k1 ( eω1 × er12 ) ] · [ er12 + k1 ( eω1 × er12 ) ] ( 8 ) v2 ( r1 ) = − gm2r [ er21 + k2 ( eω2 × er21 ) ] · [ er21 + k2 ( eω2 × er21 ) ] since the radial unit vectors will have opposite signs ( er12 = − er21 = er ) the above expressions can be written as follows v1 ( r2 ) = − gm1r [ er + k1 ( eω1 × er ) ] · [ er + k1 ( eω1 × er ) ] ( 9 ) v2 ( r1 ) = − gm2r [ − er − k2 ( eω2 × er ) ] · [ − er − k2 ( eω2 × er ) ] these individual gravitational potentials am independent of each other. However when a mutual interaction is considered in order to ensure thatan equal force is applied to each body