Define gravitational potential and give its unit. Also, derive an expression for gravitational potential at a point due to the Earth. How is gravitational P.E. related to gravitational potential?

[Image result for Define gravitational potential]
The gravitational potential (V) is the gravitational potential energy (U) per unit mass: where m is the mass of the object. Potential energy is equal (in magnitude, but negative) to the work done by the gravitational field moving a body to its given position in space from infinity.
Unit is, N Kg^-1 m