Gravitational Potential Energy
We first consider a particle with mass m moving vertically along a Y axis (the positive direction is upward). As the particle moves from point to point. the gravitational force F ~ does work on it. To find the corresponding change in the gravitational
potential energy of the particle-Earth system.
Only changes 6.V in gravitational potential energy (or any other type of potential energy) are physically meaningful. However. to simplify a calculation or a discussion we sometimes would like to say that a certain gravitational potential value.
Gravitational potential energy associated with a particle-Earth system depends only on the vertical position y (or height) of the particle relative to the reference position y = O. not on the horizontal position.