release heat
Energy is a measure of the amount of or potential for movement in something. The total amount of energy in the universe is always the same. This symmetry is called a conservation law. Conservation of energy is one of five conservation laws that govern our universe. A group of things well use the word system has a certain amount of energy. Energy can be added to a system; for instance, when chemical bonds in a burning log break, they release heat. Energy can be lost from a system; for instance, when a spacecraft burns up its energy of motion during re-entry, it loses energy and the surrounding atmosphere gains the lost energy. A closed system is one for which the total energy does not change, or is conserved . In this chapter, we will often consider closed systems, for which the total amount of energy stays the same, but transforms from one kind to another. The transfer of energy from one system to another is called Work . Work is equal to the amount of energy transferred in positive work or out negative work of a system. Work is equal to the distance the object is moved multiplied by the amount of force in the direction of its motion. The rate at which work is done is called Power .