The gravitational potential energy of a two-particle system is derived in this chapter as . Does it fallow from this equation that the potential energy for r = ∞ must be zero? Can we choose the potential energy for r = ∞ to be 20 J and still use this formula? If no, what formula should be used to calculate the gravitational potential energy at separation r?

Question

Philoid · Accepted Answer

During the derivation of the formula, for our convenience, we have decided that the particles were initially at an infinite distance from each other and are brought closer to one another. Hence, at , , and the potential at a separation of is given by

Now, instead of having a zero potential energy initially, the system is at potential of 20 J. So, we modify our equation accordingly to get