Question 63

The Correct Answer is A. **Explanation for Option A (large GM):** GM (Metacentric Height) is a key indicator of a vessel's initial stability. A **large GM** means the vessel has very high initial stability. When a vessel has high stability, it tends to right itself very quickly after being disturbed (like by a wave). This rapid righting motion results in a **quick and rapid rolling period** (short period of roll). While a quick roll might seem desirable, an extremely quick and rapid motion can be violent, leading to discomfort for passengers and crew, and potentially high stresses on the hull structure. Therefore, a quick and rapid motion is characteristic of a vessel with a large GM. **Explanation for Incorrect Options:** * **B) high center of gravity:** A high center of gravity ($KG$) typically leads to a **small GM** (or even negative GM), which results in a **tender** vessel with a **slow and sluggish** rolling period, or poor stability, which is the opposite of a quick and rapid motion. * **C) small GZ:** $GZ$ (Righting Arm) is the moment arm of the righting lever. A small $GZ$ (especially at large angles of inclination) indicates low stability, which would result in a **slow or tender** roll, or an inability to resist capsize, not a quick and rapid motion. * **D) excessive free surface:** Excessive free surface (usually caused by slack tanks) **reduces the effective GM** ($GM_{eff}$), making the vessel more tender and increasing its rolling period (a slower, sluggish motion), again the opposite of a quick and rapid motion.