Energy. What is energy? In Webster’s Unabridged Dictionary energy is defined as ‘the capacity for vigorous activity’. The law of conservation of energy states that energy can never be created or destroyed, it can only be transformed. Energy can be classified into two divisions: potential energy and kinetic energy. Potential energy is the energy stored by an object. Many forms of potential energy exist, they are gravitational potential energy, elastic potential energy, chemical potential energy, electrical potential energy, and nuclear potential energy. Gravitational potential energy(GPE) is the energy an object has stored due to its being above the Earth’s surface. GPE can be calculated by using the formula “GPE = mass(m) x gravitational acceleration(9.8 meters/second^2 or 32 feet/second^2[g]) x height(h)”. Elastic potential energy is the energy stored in the form of stress by an object that stretches. Chemical potential energy is the energy stored in the molecular bonds of an object. Electrical potential energy can be divided into two smaller groups, electrostatic potential energy and electrodynamic potential energy. Electrostatic potential energy is the amount of electrical energy stored in an object and electrodynamic potential energy is stored magnetic energy. Finally, nuclear potential energy is the amount of energy stored in the nucleus of an atom. Kinetic energy is the amount of energy an object is using. Kinetic energy(KE) can be calculated using the formula “KE = 1/2 x mass(m) x velocity(v)^2”. Potential energy plus kinetic energy equals mechanical energy which never changes. There are six different forms of energy, mechanical, electrical, light, chemical, nuclear, and thermal or heat energy. Mechanical energy, a different kind than described above, is energy involved in the physical motion of an object. Electrical energy is the energy used in the motion of electrons. Light energy is the energy used in the visible light of the electromagnetic wave spectrum. Chemical energy is the energy used by molecules during chemical reactions. Nuclear energy is the energy released when matter is turned into energy. Finally, thermal energy, or heat energy, is the energy used in the motion of matter to create heat. Friction is the most common form of thermal energy.