Hidden treasures in some simple engineering problems

Some simple engineering problems contain interesting subtleties that can serve as a springboard to gain a deeper understanding of the underlying principles and to develop a more comprehensive insight on the physics of the problems. Three examples are presented to highlight how these hidden treasures can be discovered: (1) examination of assumptions in mass diffusion in solids, (2) dimensional homogeneity in gas–liquid mass transfer equation, and (3) the Pitot tube dilemma arising from using either the momentum balance or the energy equation.