The Magnus effect explains lifting force produced by rotation; which option properly describes this phenomenon?

• A. The dragging force produced by wind on a spinning wing.
• B. 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.
• C. The magnetic interference in compasses.
• D. A type of wind shear.

Answer: (B)

The Magnus effect is the lift produced when a rotating body moves through a fluid, caused by a pressure difference created around the spinning surface. As the object spins, the surface directionally drags air with or against the free stream, speeding up air on one side and slowing it on the other. This speeds-up side has lower pressure, the opposite side higher pressure, so a net force pushes the object upward (or perpendicular to the flow). This same pressure differential around a spinning ball or cylinder explains why a baseball curves or a golf ball slices. The option describing a lifting force from rotation due to a pressure differential around a rotating cylinder captures this mechanism. The other choices describe drag, magnetic effects, or wind shear, which are not about the Magnus-driven lift.