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## Summary:

- What happens when r is zero?

## Main Question or Discussion Point

So, let's say you have a donut - shaped planet, so a second object can move right on top of the center of mass of the first object. Does force go to infinity? How about potential energy?

Or, just take one object, divide it into elements, what happens to the central element of mass within the object?

Or, just take one object, divide it into elements, what happens to the central element of mass within the object?