🔍 Key Concepts
• Six degrees of freedom of ship motion (surge, sway, heave, roll, pitch, yaw)
• Difference between linear motion (along an axis) and rotational motion (around an axis)
• Relationship between motion names and the ship’s three main axes: longitudinal, transverse, vertical
💭 Think About
• Which motions are side-to-side, forward-and-aft, and up-and-down movements of the ship’s center of mass?
• Which motions are rotations (tilting or turning) around each axis, and which are straight-line motions along each axis?
• Match the name ‘heave’ to the type of motion you’d feel on a ship in heavy seas: what direction is your body moving?
✅ Before You Answer
• Identify which axis is associated with up-and-down movement of the hull, not tilting or turning.
• Separate in your mind: surge, sway, heave are translations along axes; roll, pitch, yaw are rotations about axes.
• Double-check that the axis you choose for heave is one that describes a straight-line movement, not a rotational effect.