🔍 Key Concepts

• Study the six degrees of freedom shown in the illustration: three are straight-line (positional) motions and three are rotations about axes. • Identify which motions change the ship’s position in space (x, y, z) versus those that change its angle or attitude (roll, pitch, yaw). • Relate intact stability to whether we are talking about keeping the vessel’s position or its rotational attitude (heel/trim).

💭 Think About

• From the diagram, which labeled motions are simple up/down, side-to-side, or fore-and-aft shifts without any rotation? • Among the answer choices, separate the ones that are rotations about an axis from the ones that are translations along an axis. • Ask yourself: when naval architects talk about “positional motion stability,” do they mean controlling angles (like trim or heel) or controlling where the ship’s center of mass moves in space?

✅ Before You Answer

• Be sure you can match each motion name to its axis: surge–longitudinal, sway–transverse, heave–vertical, pitch–transverse rotation. • Confirm which of the answer choices is a rotational motion and which are positional (translational) motions. • Before choosing, verify that your selection is one of the motions that changes linear position, not one that changes angular attitude.