FAA Flight Instructor Airplane (FIA)Aerodynamics and Principles of FlightEasy
A flight instructor explains to a client that one accepted theory of lift generation is based on Newton's third law of motion. According to this theory, lift is produced primarily because the wing:
- ACreates a pressure differential due to the Bernoulli effect alone
- BUses ram air compression at the leading edge to generate an upward force
- CDeflects airflow downward, and the equal and opposite reaction pushes the wing upward
- DReduces the velocity of air below the wing to increase static pressure
Show answer & explanationAnswer & explanation
Correct answer: C. Deflects airflow downward, and the equal and opposite reaction pushes the wing upward
Newton's third law states that for every action there is an equal and opposite reaction. The wing deflects (accelerates) air downward, and the reaction to this downward force on the air is an equal upward force on the wing, contributing to lift.
Why the other options are wrong
- A. Describes Bernoulli's principle, a separate explanation of lift.
- B. Not an accepted explanation of wing lift generation.
- D. Misstates the pressure relationship used in Bernoulli's explanation.
Newton's Third Law and Lift
Lift can be explained by the wing deflecting airflow downward; the equal and opposite reaction force acts upward on the wing.
- Action: wing deflects air downward
- Reaction: equal upward force on wing
- Complements, does not replace, Bernoulli's explanation
Memory trick: Push air down, plane goes up