🔍 Key Concepts

• Six degrees of freedom of ship motion: surge, sway, heave, roll, pitch, yaw • Meaning of directional (course) stability vs transverse/longitudinal stability • Which motion is around the vertical axis as shown in the illustration

💭 Think About

• From the drawing, match each motion (pitch, sway, yaw, surge) to the axis it acts about or along • Ask yourself: which kind of motion would make the bow wander left and right from its intended course? • Eliminate the motions that only move the ship up/down or fore-and-aft without changing heading

✅ Before You Answer

• Be clear on the difference between rotational motions (roll, pitch, yaw) and translational motions (surge, sway, heave) • Identify which motion directly changes the vessel’s heading/course rather than just its position • Verify on the illustration which motion is specifically tied to the vertical axis