Which principle is commonly cited alongside Newton's third law to explain lift?

• A. Bernoulli's principle
• B. Kepler's laws
• C. Fick's laws
• D. Graham's law

Answer: (A)

Lift comes from how air moves around a wing and the forces that result from that motion. When a wing moves through the air, it deflects air downward. By Newton's third law, this downward deflection creates an equal and opposite upward force on the wing—lift. Bernoulli's principle adds the complementary piece: as air speeds up over the wing’s curved upper surface, its pressure drops, while the pressure on the lower surface remains higher, contributing to the upward force. Together, these ideas explain why there’s a net lift on the wing.

The other principles listed aren’t used to explain lift in this basic context: Kepler's laws describe planetary motion, Fick's laws describe diffusion, and Graham's law concerns gas effusion and diffusion rates.