🔍 Key Concepts

• center of gravity (G) vs. center of buoyancy (B) — what each one depends on • what happens to free surface effect when tanks are pressed full vs. partially filled • how liquid in the bottom of the ship affects stability and metacentric height (GM)

💭 Think About

• Ask yourself: when you fill double-bottom tanks completely, does the liquid inside still have room to slosh and create a free surface? How does that influence stability? • Which of the listed items (center of gravity, center of buoyancy, reserve buoyancy, freeboard) actually changes when you add weight low in the ship? • Think about which point (G or B) is related to the shape of the underwater volume, and which one is related to the distribution of weight inside the vessel.

✅ Before You Answer

• Make sure you know that double-bottom tanks are low in the ship, close to the keel • Confirm which quantity, G or B, is affected by adding or removing internal weight (like fuel or water) without changing the ship’s underwater shape very much • Eliminate any option that describes something that does not significantly change when you fill internal double-bottom tanks (hint: look at reserve buoyancy and freeboard).