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:|
|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.|