What are the two forces that affect stability?

• A. Static and Dynamic
• B. Internal and External
• C. Weight and Buoyancy
• D. Pressure and Momentum

Answer: (A)

Weight and buoyancy are the two forces that determine a boat’s stability. Weight pulls the boat downward through its center of gravity, while buoyancy pushes upward through the center of buoyancy where the water is displaced. When the boat heels, the buoyant force shifts relative to the weight, creating a restoring moment that tries to bring the boat back upright. The balance and relative positions of these two forces (and how far apart their lines of action are when tilted) define static stability, while how the boat behaves under motion, waves, and changing loads defines dynamic stability. Other concepts like static vs. dynamic describe stability behavior rather than these fundamental forces, so weight and buoyancy best capture what directly governs stability.