🔍 Key Concepts

• Free surface effect and how it changes a vessel’s stability • Difference between tanks above vs. below the center of gravity (G) • How a completely full tank behaves compared to a partially filled tank

💭 Think About

• Think about what happens to the liquid inside a tank when the vessel rolls—how does that affect stability if the tank is only partly filled? • Ask yourself: does free surface effect become more dangerous when the tank is higher or lower relative to the ship’s center of gravity? • Consider which tank condition (empty, partially full, or pressed full) minimizes the free surface effect for tanks located low in the ship.

✅ Before You Answer

• Review the definition of free surface effect and why it reduces metacentric height (GM) • Check which tank condition (empty vs. pressed up) eliminates or greatly reduces free surface • Verify that the chosen option would increase overall stability, not decrease it, for tanks below G.