Question 60 ONC01 - Master/Chief Mate Unlimited Tonnage

The Correct Answer is D **Explanation for D (The vessel's vertical axis):** Heave is defined as the vertical motion of a vessel (ship, boat, or platform) where the entire hull moves up and down parallel to the vessel's vertical axis. This motion is a translational degree of freedom, meaning the vessel changes position along that axis without rotation. **Why the other options are incorrect:** * **A) The vessel's centerline axis:** While the vertical axis is sometimes referred to in relation to the vessel's centerline, the centerline axis itself usually refers to the longitudinal axis (running bow to stern) or the axis around which yaw occurs. Heave is movement *along* the vertical axis, not the centerline axis in this common definition. * **B) The vessel's transverse axis:** Motion along the transverse axis (side-to-side, or port to starboard) is called **Sway**. * **C) The vessel's longitudinal axis:** Motion along the longitudinal axis (forward and backward, or bow to stern) is called **Surge**.