Pitched Wings & Lift

# Newton's Laws, Pitched Wings, and "Lift"

The aerodynamic lift produced by the motion of a pitched, or tilted, wing moving through air can be understood directly through Newton's Laws of Motion.

Consider a pitched wing moving through stationary air at a constant speed, v. From the point of view of the wing, it is not moving. Rather, the air is rushing by it with net speed v in the opposite direction.

Air is made up of many molecules and atoms that follow Newton's Laws of Motion. Newton's second law says that each molecule hitting the wing experiences an acceleration proportional to the force of contact, and inversely proportional to its own mass.*

Newton's third law tells us that the wing experiences a force that is equal in size but opposite in direction to that felt by the molecule.** While an individual collision of a molecule has little effect, putting billions of billions of impacts together each second does have a real effect - known as lift.

Aerodynamic lift of this type relates to how airplanes can fly. It is commonly experienced during takeoff, landing, and stunt maneuvers like flying upside down. And, it is the primary source of lift during level flight.

The Bernoulli effect, which many people believe is the main source of aerodynamic lift, contributes to a lesser degree to the overall lift of an airplane. Its contribution comes from the airfoil shape of the wing.

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* Force equals mass times acceleration or F = ma, where mass is constant. Dividing both sides by the mass m and solving for the acceleration we obtain a = F/m.

** For every action there is an equal and opposite reaction.