đ Key Concepts
⢠Ship motions and axes: surge, sway, heave, roll, pitch, yaw
⢠Difference between linear motions (along an axis) and rotational motions (about an axis)
⢠Meaning of longitudinal, transverse, and vertical axes on a vessel
đ Think About
⢠First decide: is heave a motion that moves the ship in a straight line, or one that rotates/tilts the ship?
⢠Visualize the three main directions on a ship: frontâback, sideâside, and upâdown. Along which of these does heave happen?
⢠Match each ship motion name (surge, sway, heave) to one of the three straight-line directions; then pick the axis that describes that direction.
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Before You Answer
⢠Be clear which axis means up-and-down direction on a vessel
⢠Separate in your mind motions along an axis (surge, sway, heave) from motions about an axis (roll, pitch, yaw)
⢠Verify that the axis you choose correctly represents the vertical direction relative to the ship, not just its length or width