Unveiling the Physics of Partial Differential Equations with Heuristics

Heuristic arguments and order of magnitude estimates for partial differential equations highlight essential features the physics they describe. We present estimates, their limitations, three classic second PDEs mathematical (wave, heat, Laplace equations), first transport equations, two nonlinear wave equations. It is beneficial to expose beginning student these considerations before jumping into more rigorous mathematics. Yet simple are missing from textbooks.