Sidewise force of the propeller tends to throw a vessel's stern to the right or left, depending on rotation. This force is caused by __________.

Correct Answer: Option A — torque from the velocity and angle at which the surrounding water impinges upon the propeller blades

Sidewise force results from the unequal pressure distribution across the propeller disc. This is caused by the varying velocity and angle at which water impinges on the blades during rotation. This torque effect creates a lateral force that pushes the stern, a fundamental principle in single-screw vessel handling.