On This Page
Overview
Conservation of energy is one of the most important principles in physics. In an isolated system, total energy remains constant even as energy changes form or moves between objects.
Mechanical Energy
Mechanical energy is often treated as the sum of kinetic energy and potential energy. In ideal systems with only conservative forces, total mechanical energy remains constant.
Energy Transfer
Energy can transfer through work, heat, waves, radiation, electric currents, and material motion. In mechanics, work is a major way energy crosses a system boundary.
Energy Transformation
Energy transformation occurs when energy changes form. Chemical energy can become thermal energy and mechanical motion, while gravitational potential energy can become kinetic energy.
Conservative and Nonconservative Forces
Conservative forces allow mechanical energy to be stored and recovered. Nonconservative forces, such as friction, transform mechanical energy into other forms such as thermal energy.
Energy Accounting
Energy conservation is a form of accounting. A careful analysis identifies the system, initial energy, final energy, external work, losses, and stored energy changes.
Real-World Systems
Real systems often transform energy into several forms at once. A car engine produces mechanical motion, heat, sound, vibration, and exhaust energy.
Common Mistakes
A common mistake is saying energy is lost when mechanical energy decreases. Energy is transformed or transferred, not destroyed.
Applications
Conservation of energy is used in mechanics, thermodynamics, electricity, chemistry, engineering, astronomy, biology, and environmental science.
Why This Matters in Physics
Conservation of energy gives physics a powerful organizing principle for tracking physical change across many systems.