Gravitational Potential Energy
Gravitational potential energy (GPE) is defined as the energy possessed by an object and the earth (or other planet or mass) based upon the object's location within the earth's (or other object's) gravitational field. We can define any point within a gravitational field as having a GPE of zero, and typically, when we are dealing with an object located within the earth's gravitational field, we set GPE equal to zero at the surface of the earth. Thus, we say the formula for the gravitational potential energy possessed by an object/Earth system is equal to the mass of the object multiplied by the magnitude of the acceleration due to gravity multiplied by the distance of the object above the surface of the earth.
Note: We can consider a system to have gravitational potential energy relative to the surface of the earth ONLY if we include not only the object in our system but also the earth as belonging in the system. We say that the object/Earth system has gravitational potential energy.
Note: We can consider a system to have gravitational potential energy relative to the surface of the earth ONLY if we include not only the object in our system but also the earth as belonging in the system. We say that the object/Earth system has gravitational potential energy.
If we set gravitational potential energy equal to zero at the surface of the earth, then we say that any object which is located below the surface of the earth has a negative gravitational potential energy.