🔍 Key Concepts

• Six degrees of freedom of vessel motion (surge, sway, heave, roll, pitch, yaw) • Difference between linear (straight-line) motion and rotational (angular) motion • Which axis is considered the vertical axis on a ship

💭 Think About

• Identify which of the options are types of motion about an axis (rotational) versus along a straight line (translational). • Recall the standard names for motion about the longitudinal axis, transverse axis, and vertical axis. • Match each choice to either rotation or straight-line movement, then focus on the one that fits rotation around the vertical axis.

✅ Before You Answer

• Confirm which motion is rotational about the vertical axis (not longitudinal or transverse). • Verify which term (from the options) is actually a linear motion along the fore‑and‑aft axis and therefore cannot be correct. • Be sure not to confuse rotational motion names (roll, pitch, yaw) with hull shape or condition terms like hog/sag.