What is the Righting Arm?

• A. Distance between the forces of buoyancy and gravity
• B. The distance from the keel to the weather deck
• C. The height of the center of gravity
• D. The moment required to restore upright

Answer: (A)

The question is about the righting arm, which describes the lever that creates a restoring moment when a vessel heels. When a ship tilts, the buoyant force shifts to the lower side while gravity continues to act downward through the center of gravity. These two forces then form a turning moment because they act along two different lines. The distance between those lines of action, measured horizontally, is the righting arm (often called GZ). The larger this lever arm, the greater the restoring moment, because the moment is equal to weight times GZ (M = W × GZ) and tends to bring the ship back upright.

So, the right answer is the distance between the lines of action of buoyancy and gravity. The other concepts are different: the distance from keel to weather deck is a structural measurement, the height of the center of gravity affects stability but is not the righting arm itself, and the restoring moment is the product of weight and the righting arm, not the arm by itself.