Got it. At least one of the masses must be a point mass and then only when considering the force exercised on it by a collection of dispersed masses. Then the collection of dispersed masses can be lumped around the center of mass and only for great distances.
Thanks
You answered while I was typing Thanks
Do not remember exactly, but there was some mention of "spherical symmetry".
Now a bar bell O======O does not seem to have spherical symmetry but anything missing to a full sphere could (not really sure) be seen as a collection of bar bell each behaving...
I like math and physics and sometimes I pose myself a question for which I try to get an answer.
For a more practical hobby I build model engines
Use to design Power Supply and telephone equipment like modems, trunk interfaces and signaling apparatus.
Normalizing respect m, M, R and k then the normalized force for the case of the bar bell body aligned with the direction of R become Fn = 1/(1+x)^2 + (1-x)^2 is a vectorial sum but in this case the vectors are aligned
We can assume x<<1 but is not really material to the problem
For...