CBSE Class 11-science Answered

A ball which is spinning drags air along with it. If the surface is rough more air will be dragged. The layer above the ball moves in a direction opposite to that of a spinning ball, so the resultant velocity decreases, and hence, pressure increases in accordance with Bernoulli's principle.

The layer below the ball moves in the direction of spin and the resultant velocity increases thereby decreasing the pressure. Due to the difference of pressure on the two sides of the ball, the ball curves downward in the direction of spin.