Which statement about free surface is TRUE?

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🔍 Key Concepts

• Free surface effect (FSE) and its impact on GM (metacentric height) and stability • Meaning of pocketing in tanks and when it occurs (small or large angles, nearly full vs slack tanks) • Relationship between permeability / percentage of free liquid surface and the magnitude of free surface effect

💭 Think About

• Compare how a liquid moves in a nearly full tank versus a slack (partially filled) tank when the ship heels. In which case can a continuous free surface form and shift more? • Think about whether a denser liquid (higher specific gravity) produces more or less free surface moment than a lighter liquid in the same tank dimensions. • Ask yourself: if more of the compartment volume actually becomes free liquid surface when the ship heels (higher surface permeability), does that increase or decrease the free surface effect?

✅ Before You Answer

• Be clear on the definition of pocketing: does it reduce or increase the effective free surface as the angle of heel grows? • Verify which condition creates the worst loss of GM: a tank almost full, a tank pressed up, or a slack tank. • Check that statements about surface permeability percentages are consistent: more effective free liquid surface area should mean greater free surface effect, not less.

🔍 Key Concepts

💭 Think About

✅ Before You Answer