Rick Cavallaro wrote:

On Oct 1, 6:38 am, Ronald Raygun wrote:

I apologise for my earlier misunderstanding, which came from being
fixated on the boat example being driven by a water propeller using
power harvested from an air turbine. I see that in the case of the
land based car you're discussing it is not using the air screw as a
source of power with which to drive the wheels, but the wheels as a
source of power with which to power the air propeller.

I don't doubt that this is possible, but I believe your analysis below
is wrong. I offer a corrected version below.

Well, you're making progress. I suspect if you'll continue a rational
discussion with JB he'll be able to convince you that your "corrected"
analysis is in fact wrong.

I'll approach what he has to say with an open mind.

I would point out, though, that my result (of the prop requiring 3/4 hp)
means that 1/4 hp is available to be dissipated on losses and on the
car's air resistance etc. Since we are considering the car as being in
steady state motion, no power is needed to accelerate it.

This spare 1/4 hp has to come from somewhere, and it is from the wind
being slowed down, its kinetic energy being transferred into those
losses. Right?

It is no coincidence that the kinetic energy of 11.7 lb of air at
27.5 ft/s is exactly 1/4 hp s.