🔍 Key Concepts

• Free surface effect and how liquids in partly filled tanks move when a vessel heels • Relationship between free surface effect and transverse stability / metacentric height (GM) • Which listed properties (rolling period, metacentric height, waterplane area, vessel's draft) are directly linked to stability and free surface

💭 Think About

• When a tank is only partly full, what happens to the center of gravity as the ship rolls? Does that help or hurt stability? • If you reduce free surface effect, are you making the ship more stable or less stable? Which option corresponds to that change? • Which of the four choices is most directly tied to how "stiff" or "tender" a ship feels in a roll?

✅ Before You Answer

• Identify which choice is a primary stability parameter affected by free surface effect, not just a secondary result like motion feeling • Recall that free surface effect tends to raise the ship’s center of gravity; think about which parameter that change directly influences • Make sure the option you select is something that changes when you go from many slack tanks to all tanks pressed full or empty