Lift (force)

Lift is the component of fluid force perpendicular to an object's motion through the fluid. Around a wing, pressure differences and redirected airflow produce this force.

Kutta–Joukowski theorem: A theorem relating lift per unit span on a two-dimensional body to fluid density, circulation, and flow speed. It gives a precise relation between circulation around a wing and its lift.
Fluid: A substance that flows and deforms continuously under applied shear stress, including liquids and gases. Lift is a force exerted by a flowing fluid on an immersed body.
Aircraft wing: A fixed aerodynamic surface that generates forces supporting and controlling an aircraft in flight. Its lift must balance weight during steady, level flight.
Drag (physics): The component of fluid force parallel and opposite to an object's motion relative to the fluid. Drag acts along the flow direction, while lift is defined perpendicular to it.
Circulation (fluid dynamics): A measure of the net rotational flow around a closed curve in a fluid. Circulation around an airfoil provides one mathematical account of lift.
Pressure: Force per unit area exerted normally on a surface. Unequal pressure over a wing surface contributes to the net aerodynamic force.
Lift coefficient: A dimensionless quantity expressing lift relative to dynamic pressure and a reference area. It lets designers compare lift across speeds, sizes, and operating conditions.
Thrust: A force that propels an object, commonly produced by expelling mass or interacting with a surrounding medium. Thrust propels an aircraft; lift supports it against gravity.
Bernoulli's principle: A relation stating that, under specified steady-flow conditions, higher fluid speed corresponds to lower static pressure along a streamline. Pressure differences associated with airflow speed contribute to lift on a wing.
Viscosity: A measure of a fluid's resistance to deformation and flow. Viscosity shapes near-surface airflow and influences separation and stall.

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