What is the Magnus effect?

• A. The drag caused by propeller wash.
• B. A type of magnetic interference in compasses.
• C. Lifting force produced when a rotating cylinder produces a pressure differential; this is the same effect that makes a baseball curve or a golf ball slice.
• D. An effect describing stall characteristics at high angle of attack.

Answer: (C)

The lifting force arises when a spinning object moves through air, creating a pressure difference around its surface. The rotation adds velocity to the air on the side that moves with the flow and subtracts velocity on the opposite side. Faster air on one side lowers pressure there, while slower air on the other side raises pressure. This pressure differential pushes the object upward (perpendicular to the oncoming flow), producing lift. This is the Magnus effect. It explains why a spinning baseball can curve and why a spinning golf ball can slice or curve in flight. The other options describe different phenomena (propeller-induced drag, magnetic interference with compasses, or stall behavior) that don’t involve this spin-induced pressure differential.