Different point
B540
Yup that's true - but a different thing. If the 'wind' changes then you recieve or lose energy. but if you run circles inside a cruise ship - you cant tell which way the ship is travelling - no kinetic energy difference (relative to the ship)
Surprisingly
Autorotation downwind is, in energy terms, more useful - since the wind sheer 'adds energy' - from the reduced tail wind (equivalent to increased headwind)
WHO WAS GIVING THE LECTURE referred to AT THE BEGGINING OF THE POST - was it military?