The gravitational potential energy *U* (written as *U*_{}
if it needs to be distinguished from other potential energy) of
an object near the surface of the earth is the mass of the object
*m* times the gravitational force constant times the height *y*
of the object above a specified reference level.

Pitfall Avoidance Notes: |
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1. | This expression is an approximation to the universal-law-of-gravitation expression for gravitational potential energy. It is a good approximation within 20 km of the surface of the earth. Beyond that, one should use the universal-law-of-gravitation expression for gravitational potential energy. | |

2. | Don't use this expression without first having clearly established a reference level. The expression is used in conservation-of-energy and work-energy problems. Solutions to both kinds of problems must include before and after diagrams. Establish the reference level in the before and after diagrams. |