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Lift is created by deflecting a flow of air and drag is generated on a body in a wide variety of ways. From Newton's second law of motion, the aerodynamic forces on the body (lift and drag) are directly related to the change in momentum of the fluid with time. The fluid momentum is equal to the mass times the velocity of the fluid. Since the air moves, defining the mass gets a little tricky. Modern aerodynamicists relate the effect of mass on lift and drag to the air density. At the time of the Wright brothers, the effect of mass was included in the Smeaton pressure coefficient. In both systems, the lift and drag depend on the square of the velocity.

The velocity used in the lift and drag equations is the relative velocity between an object and the flow. Since the aerodynamic force depends on the square of the velocity, doubling the velocity will quadruple the lift and drag.

Let's investigate the dependence of lift on velocity using a Java simulator.