<nod> Big M, small change in V, for efficiency.
Tie it into energy cost, 1/2mv^2 and pretty much everything about propulsive efficiency drops into place. Not to mention induced drag versus airspeed.
Trouble is, to really 'get' it, the student needs to be fluent with the conceptual differences between momentum and kinetic energy. Unfortunately many think that because they both have an M and a V in them they are basically interchangeable
pb