Jdsk wrote: ↑13 Nov 2022, 9:35pm
The power required to overcome the aerodynamic drag of an object moving through the air and its relation to relative air velocity is independent of the means of propulsion and whether some part of the object touches the ground or not.
The drag force is:
Screenshot 2022-11-13 at 21.31.20.png
The power is:
Screenshot 2022-11-13 at 21.32.24.png
where that velocity term is the velocity of the object relative to the fluid throughout.
...
The force and the power required depend on the molecules of the fluid and how big the object is and what shape the object is and how fast it hits the molecules. None of these are affected by the means of propulsion.
Jonathan
That is the power which is transferred to the air. It is not equal to the power expended by the cyclist.
My argument is true in two special cases. Yours fails in one of them, in that we have been arguing solely about the power expended by the cyclist.
Case (1): No headwind - still air. Both arguments true.
Case (2): Stationary trike in headwind - cyclist stops trike rolling backwards by pressing down on forward pedal. Cyclist does no work because pedal is not moving downwards - no work, no power.
There are texts on dynamics which carefully define force, work, energy and power. They are available in book shops, libraries and online.