Where is Gravitational Potential Energy Zero?

[sphyics]

P.E of a body in the graitational field of planet is zero. The body must be at:

a) Centre of planet b) on the surface of planet c) Infinite distance d) At distance equal to radius of earth


how to think over the problem.

 

[berkeman]

P.E of a body in the graitational field of planet is zero. The body must be at:

a) Centre of planet b) on the surface of planet c) Infinite distance d) At distance equal to radius of earth


how to think over the problem.

Potential energy is relative to some datum. You can define your datum wherever you want.

 

[Doc Al]

how to think over the problem.

As berkeman says, you need a reference point. I suspect that they want you to use the standard formula for the gravitational PE between two bodies, which has a built-in reference point. What is that formula?