Table 7.1: Summary of the symbols and units of the quantities used in Energy Units Quantity Symbol Unit S.I. Units Direction Work W J N.m or${\displaystyle kg.m^{2}.s^{-2}}$ -- Kinetic Energy EK J N.m or${\displaystyle kg.m^{2}.s^{-2}}$ -- Potential Energy EP J N.m or${\displaystyle kg.m^{2}.s^{-2}}$ -- Mechanical Energy U J N.m or${\displaystyle kg.m^{2}.s^{-2}}$ --

Principle of Conservation of Energy: Energy is never created nor destroyed, but merely transformed from one form to another.

Conservation of Mechanical Energy: In the absence of friction, the total mechanical energy of an object is conserved.