From examining the the GPE equation....
The point x, where GPE is minimum, is the point where this force Fob acts will always be greater than Orbs. This conclusion is drawn from the fact that the negative area under the gravity curve is compensated for by the positive area under the curve on the far side. We started with a higher gravity body on the near side.
Orbs is the point on the surface of the Moon where gravity is 1.62 ms-2,.. It should act at the C.G. If this force does not act at the C.G., then a torque will develop and the body will spin. If the body is orbiting clockwise, (an arbitrary a reference) then a point of action less than the C.G. will cause the body to spin anti-clockwise and a point of action beyond the C.G. will cause the body to spin clockwise.
This spin creates a Rotational Kinetic Energy component that will decrease the GPE plateau so that the drop from the plateau value will find a new x position on the x-axis. A rise in GPE will effect a new position in the positive x direction, whereas a decrease in GPE will cause the new intercept on the x-axis to be less than the current position. GPE rises on a decrease in spin speed and falls with a increase in spin. The system spins up or down till Fob finds the C.G. No external forces are acting on this two body system, and so the total energy of the system is conserved. The present of some other gravitational field may cause Fob to shift and so causes a body to spin up or spin down. The passage of Gravitation Waves, for example may cause a planet to spin.
Yes, Fob is on the line through the C.G. A spin develops because of inertia. The body is already in circular motion, because Orbs is constrained to be a fixed value and kinetic energy of the system is not necessarily zero.
The same phenomenon can be seen when a magnet pulls on a metal ball suddenly while guiding it in circular motion. Whipping the metal ball into a spin.
Fob develops because GPE seeks a minimum and remains a minimum because there are no external forces acting on the system. A change in orbital configuration will require energy input; in orbital motion the system total energy remains constant still. Fob is not doing any work.
This then is the mystery of spinning planets. Did I just discovered a new force or what?! I have found the Force.
