🔍 Key Concepts
• Free surface effect (FSE) and how it affects a vessel’s KG and stability
• The formula for free surface correction (FSC) and where the moment term appears
• Difference between displacement and moment (weight vs. weight × distance)
💭 Think About
• Ask yourself: when we talk about a “correction to KG,” are we dealing with a pure distance, a pure weight, or a moment (weight × distance)?
• Which quantity, when divided by the vessel’s displacement (total weight), gives a distance that can be added to or subtracted from KG?
• Look at each option and decide: which one has the correct physical units so that, after dividing by displacement, the result is in meters/feet (a KG correction)?
✅ Before You Answer
• Make sure the numerator has units of moment (ton-meters, ft-tons, etc.), not just weight or distance alone.
• Verify that displacement is in units of weight (long tons, metric tons, etc.), so that moment ÷ weight = distance.
• Eliminate any option that would give you the wrong units after division (e.g., distance, pure weight, or a dimensionless number instead of a distance).