Total Time Derivatives, Again
Thomas E. Phipps
Treatments of the invariant total time derivative by Mocanu [4] and by Post [3] are compared and found to be in substantial agreement, despite their different mathematical appearances. It is argued that the line integral approach is better adapted to electrodynamics and the surface integral approach to hydrodynamics. The line integral seems to yield a physically satisfactory invariant form of the electrodynamic force law based on the total time derivative.
