Question

How do you identify the zero reference position for calculating mechanical potential energy? What is the most common zero reference position for system that has gravitational potential energy?

Answer 1

The zero reference position should be the position the system has the least potential energy. As an object falls, its potential energy is converted into kinetic energy. Gravity's ability to do work (potential energy) reaches zero when it hits the ground and stops falling, hence the ground is the most common zero reference position.