Great Idea 6

Idea 6: Conservation of energy
    

Though the conservation of energy is of fundamental importance in physics. The law of conservation of energy states that energy can never be created or destroyed; it can only be transferred and converted into different forms. This is one of the most important unifying principles of physics.  We constantly experience its effects in our day to day lives. Isaac Newton’s Principia was published in 1687, marking the start of quantitative theoretical physics, but conservation of energy was not established until the 1840s, over 150 years later.

      In the 1600s, greats scientists such as Christiaan Huygens and Gottfried Wilhelm Leibniz recognized that something besides momentum seemed to be conserved in the collisions of moving bodies; Leibniz called it the “vis viva” (living force) of the system.  Émilie du Châtelet (1706 – 1749) first proposed and tested the hypothesis of the conservation of total energy, as distinct from momentum. In 1798, Count Rumford (Benjamin Thompson) performed measurements of the frictional heat generated in boring cannons, and developed the idea that heat is a form of kinetic energy.
The mechanical equivalence principle was first stated in its modern form by the German surgeon Julius Robert von Mayer in 1842. Meanwhile, in 1843, James Prescott Joule independently discovered the mechanical equivalent in a series of experiments. Thus it was firmly established that heat is a form of energy and the total energy is conserved.

The law of conservation of energy is important wherever energy is involved. At power plants, chemical and mechanical energy are transformed into electrical energy. Kitchen appliances transform electrical energy into thermal and mechanical energy. Automobile engines transform chemical energy into thermal and mechanical energy. In each of these cases, the total energy remains conserved.