What is the primary purpose of a rudder on a ship?

The primary purpose of a rudder on a ship is to steer the vessel. The rudder is an essential control surface typically located at the stern (rear) of the ship, and it enables directional movement. When water flows over or around the rudder, it creates a force that causes the ship to turn left or right, allowing the operator to navigate and maneuver the vessel effectively.

The rudder does not control speed; that function is primarily handled by the engine and propeller system. While stabilization is important in maintaining the hull's position and reducing unwanted rolling or pitching, it is more the role of other components of the ship, such as stabilizers or hull design. Increasing buoyancy is related to the ship's overall design and shape, which ensures that it floats on water; however, it is not a function of the rudder. Therefore, the correct answer emphasizes the rudder's pivotal role in steering, which is crucial for safe and effective navigation.