Concerning the start-up of plain bearings utilizing the three modes of hydrodynamic lubrication, what is the correct sequence of modes from start-up through coming up to operational speed?

Correct Answer: Option B — First boundary lubrication, followed by mixed-film lubrication, then finally full-film lubrication.

Hydrodynamic lubrication begins with boundary lubrication, where metal-to-metal contact occurs at low speeds. As speed increases, mixed-film lubrication provides partial separation. Finally, at operational speed, a full-film of lubricant completely separates the surfaces, minimizing friction and wear, consistent with standard tribological principles applied to shipboard rotating machinery.