Final answer:
The student's question is about the engineering practice of using an inert gas to purge air from a pipe, related to fluid mechanics principles, and involves calculations that may be specific to their unique project requirements.
Step-by-step explanation:
The subject in question addresses the clearance of air from a pipe using an inert gas, which pertains to a branch of engineering often concerned with fluid dynamics. While the exact dimensions (NPS size and length) required to answer the student's question have been omitted, we can infer that the parameters would be set by the particular project or industry standards. However, in similar scenarios, determining the usage of inert gas for purging depends upon the volume of the pipe and the type of gas or liquid that will eventually occupy the system.
Given the additional reference questions, it is likely this student is dealing with questions relating to fluid mechanics, which is a sub-discipline of engineering and physics. Fluid mechanics deals with the behavior of liquids and gases in motion, as illustrated by the given examples that involve pressure calculations, flow rates, and Reynolds numbers.