Energy and Momentum

Key Knowledge

• 1Energy is the ability to do work or cause change. It exists in many forms, including kinetic, potential, thermal, chemical, and electromagnetic.
• 2The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another.
• 3Momentum is the product of an object's mass and velocity. Like energy, momentum is conserved in closed systems.
• 4When objects collide, both energy and momentum are conserved, though energy may change forms (e.g., from kinetic to thermal).
• 5Power is the rate at which energy is transferred or work is done, measured in watts (joules per second).

Historical Context

The Conservation Principles

The concepts of energy and momentum conservation have deep historical roots. In the 17th century, Gottfried Leibniz introduced the concept of 'vis viva' (living force), an early version of kinetic energy. Later, scientists like James Joule demonstrated that different forms of energy (mechanical, electrical, thermal) could be converted into one another. By the 19th century, the law of conservation of energy was firmly established as one of physics' most fundamental principles, later expanded by Einstein's famous equation E=mc², which showed that even mass is a form of energy.

Key Figures