5.1.2—The principle of conservation of energy

The principle of conservation of energy says total energy is constant: energy is transferred between stores, not created or destroyed.

Define the system boundary and identify where energy enters, leaves or changes store. Include useful and dissipated pathways in a complete account.

A falling object transfers gravitational potential energy mainly to kinetic energy, then to thermal energy through drag.

“Wasted” energy has not vanished; it has usually spread into less useful thermal stores.