🔍 Key Concepts

• Center of gravity (G) movement when weights are shifted or liquids move in a tank • Effect of free surface in partially filled tanks on vessel stability and virtual rise of G • Difference between a real rise of G (actual weight moved up) and a virtual rise of G due to free-surface effect

💭 Think About

• Which choices involve liquid in a tank, and which involve solid weights being shifted or lifted? • How does a partially filled tank with a free surface affect stability compared to a tank that is either pressed full or completely empty? • In which situation does the free-surface effect become larger, and in which situation does it become smaller or disappear?

✅ Before You Answer

• Identify which options increase the free-surface effect and which reduce or eliminate it • Decide whether virtual rise of G is associated with the behavior of liquids or the movement of solid weights alone • Check your stability notes: does emptying or completely filling a tank increase or decrease the free-surface correction?