Bypass ratio the velocity of a very large volume and consequently mass of air produces a very large change in momentum and thrust: thrust is the engine's mass flow (the amount of air flowing through the engine) multiplied by the difference between the inlet and exhaust velocities in—a linear relationship—but the kinetic energy of the exhaust is the mass flow multiplied by one-half the square of the difference in velocities. A low disc loading (thrust per disc area) increases the aircraft's energy efficiency, and this reduces the fuel use. The Rolls–Royce Conway turbofan engine, developed in the early 1950s, was an early
Mass–energy equivalence Mass–energy equivalence In physics, mass–energy equivalence states that anything having mass has an equivalent amount of energy and vice versa, with these fundamental quantities directly relating to one another by Albert Einstein's famous formula: formula_1 This formula states that the equivalent energy () can be calculated as the mass () multiplied by the speed of light ( = about m/s) squared. Similarly, anything having energy exhibits a corresponding mass given by its energy divided by the speed of light squared . Because the speed of light is a very large number in everyday units, the formula implies that even an