-, electrical, or other forms. According to the law of conservation of energy, the total energy of a system remains constant, though energy may transform into another form. The SI unit of energy is the joule (J) or newton-meter (N * m).

t. The principle of density was discovered by the Greek scientist Archimedes. To calculate the density (usually represented by the Greek letter "rho") of an object, take the mass (m) and divide by the volume (v): rho = m vThe horsepower (hp) is a unit in the foot-pound-h kilowatt s (kW).