🔍 Key Concepts

• Free surface effect in partially filled tanks • How liquids moving in a tank affect a ship’s center of gravity and stability • Which issues are directly caused by liquid shift vs. separate structural or environmental concerns

💭 Think About

• Think about what happens to the vessel when liquid in a wide tank can move freely from side to side—does that mainly affect strength, stability, or pollution? • Ask yourself: which of the listed problems is an immediate, direct consequence of the liquid’s ability to shift as the vessel heels or rolls? • Consider whether each option is a primary reason for avoiding free surface effect, or more of an indirect/secondary concern.

✅ Before You Answer

• For each choice, ask: Is this a direct effect of liquid shifting in a partially filled tank? • Recall that free surface effect changes the transverse stability by influencing the metacentric height (GM)—which answer best matches that? • Check whether "all of the above" is justified: do all three items truly result specifically from free surface effect, or are some related to other ship behaviors or regulations?