Which point is the line through which the weight of the ship's structure and contained load acts vertically downward?

• A. Center of Gravity
• B. Center of Buoyancy
• C. Metacenter
• D. Plimsoll

Answer: (A)

Weight acts along a vertical line through the ship’s center of gravity. The center of gravity is the point where all the ship’s mass can be considered to be concentrated, so the resultant weight force acts downward through that point. The buoyant force, in contrast, acts upward through the center of buoyancy (the centroid of the displaced water) and shifts as the ship heels. The metacenter is the point used to assess stability when the ship tilts, and the Plimsoll line marks the maximum permissible loading. Since the weight’s line of action is the vertical line through the center of gravity, that is the correct concept.