Which statement accurately describes the 6 degrees of freedom of a vessel on water?

Which statement accurately describes the 6 degrees of freedom of a vessel on water?

• A. The six motions about three axes: Roll, Pitch, and Yaw
• B. The six motions about three axes: longitudinal (X), lateral (Y), and vertical (Z)
• C. The four motions about two axes
• D. There are no motions on calm water

Answer: (B)

At the heart of this concept is that a vessel can move in three directions (forward/back, side to side, up/down) and can rotate about three perpendicular axes (tilt side to side, tilt forward/back, and spin left/right). Those three axes are called longitudinal (X) along the boat’s length, lateral (Y) across the beam, and vertical (Z) up and down. Taken together, this gives six degrees of freedom: three translations (surge, sway, heave) and three rotations (roll, pitch, yaw) about those axes. The statement that describes six motions about the three axes, with X, Y, and Z defined as longitudinal, lateral, and vertical, is therefore correct. The other options misstate either the number or type of motions or the axes, or claim there are no motions on calm water.

At the heart of this concept is that a vessel can move in three directions (forward/back, side to side, up/down) and can rotate about three perpendicular axes (tilt side to side, tilt forward/back, and spin left/right). Those three axes are called longitudinal (X) along the boat’s length, lateral (Y) across the beam, and vertical (Z) up and down. Taken together, this gives six degrees of freedom: three translations (surge, sway, heave) and three rotations (roll, pitch, yaw) about those axes. The statement that describes six motions about the three axes, with X, Y, and Z defined as longitudinal, lateral, and vertical, is therefore correct. The other options misstate either the number or type of motions or the axes, or claim there are no motions on calm water.