🔍 Key Concepts

• Free surface effect and how liquid in a slack (partially filled) tank shifts when the vessel heels or rolls • How moment of inertia of the liquid surface changes with the dimensions (length/width) of the tank • The difference between properties of the vessel as a whole (draft, displacement) vs. properties of the tank and liquid

💭 Think About

• Ask yourself: which option directly affects how FAR the liquid can move side-to-side inside the tank when the ship heels? • Which factor will change the heeling moment caused by the shifting liquid, rather than just changing how heavy or deep the ship is overall? • Which answer choice is about the geometry of the liquid surface in the tank, not about the ship’s overall size or loading condition?

✅ Before You Answer

• Identify which choices are about the ship’s characteristics (draft, displacement) versus the tank’s characteristics • Focus on the factor that alters the width/area of the liquid surface that can shift, because that increases the free surface moment • Verify which option would make the free surface moment of inertia larger, thereby worsening stability when the vessel is in motion