Which term is identified as a stability reference point?

• A. Metacenter
• B. Gravity
• C. Buoyancy
• D. Keel

Answer: (A)

The stability reference point is the metacenter. When a vessel heels even a small amount, the center of buoyancy shifts to the low side, and the line of action of buoyant force changes. The metacenter is the imaginary point where this buoyant force would intersect the vessel’s vertical centerline if the hull were rotated slightly. The distance from the center of gravity to this point—metacentric height—determines stability: a positive distance means the weight and buoyancy create a righting moment that pushes the ship back upright; a negative distance means a destabilizing moment that can lead to capsizing. Gravity and buoyancy are forces involved in the stability balance, while the keel is a physical hull feature, not the reference point used to assess initial stability.