🔍 Key Concepts

• Free surface effect and how it reduces a vessel’s transverse stability (GM) • Difference between amount/weight of liquid vs. the shape/area of the liquid surface • Why tank breadth and surface dimensions matter when the ship heels

💭 Think About

• When a tank is only partially full, what actually moves as the vessel heels: the total weight of liquid, or the center of gravity of the liquid surface? • If you have two tanks with the same volume of liquid but different surface areas (one long and narrow, one short and wide), which one will cause a bigger loss of stability when the ship heels? Why? • Which tank feature directly affects how far the liquid’s center of gravity can travel sideways when the ship heels?

✅ Before You Answer

• Focus on the geometry of the free liquid surface, not just how much liquid is in the tank • Ask: which option relates most to the area/shape of the top liquid surface that can move side-to-side? • Remember: the most critical factor for free surface effect is what changes the transverse moment of inertia of the liquid surface