A spinning ball moves forward through air. On the upper side of the ball, the motion of the ball's surface is in the same direction as the surrounding airflow, while on the lower side it is in the opposite direction. In an idealized Bernoulli explanation of the Magnus effect, which statement is correct?
Options

Question

A spinning ball moves forward through air. On the upper side of the ball, the motion of the ball's surface is in the same direction as the surrounding airflow, while on the lower side it is in the opposite direction. In an idealized Bernoulli explanation of the Magnus effect, which statement is correct?

Options

G1 Physics · Accepted Answer

Rotation modifies the relative air speed around opposite sides of the ball. On the side where the surface motion assists the airflow, the air speed becomes larger. In the simplified Bernoulli picture, higher speed → lower static pressure. Therefore the upper side has lower pressure in the situation described. The pressure difference produces a transverse force called the Magnus force. Correct option: B.