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Mess with your minds: A wind powered craft going faster than a tail wind speed.
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bdunham7:

--- Quote from: electrodacus on September 03, 2021, 12:27:37 am ---Check post #351 and I explained why it is very different yesterday.
The intermediary case b) should make it clear why there is a difference between a) and c)
Treadmill is not moving relative to ground the pushed treadmill is clearly moving relative to ground.

--- End quote ---

You didn't explain anything.  You just asserted that it was true and didn't even wave your hands much.

In each case, assuming no slippage, the surface of the treadmill will provide force tangential to and at the circumference of the wheel sufficient to rotate the wheel at 4m/s.  The amount of that force depends on the amount of reaction force that is provided by loading the generator, friction, etc.  If it there is no load or friction, the force will be zero--in all 3 cases.  If there is a load, the force will be whatever force is required to rotate the wheel and that force will be transmitted to the axle and thus the body of the car.  Those two forces, combined with the two resultant reaction forces will also result in torque on the body of the car, which could be a trap for any would-be demonstrator!  But again, this is all the same in all 3 cases.  As I said in my earlier car, all of these interactions are mediated by forces.  So if you think there is a difference between the three cases, show us what additional force is involved.
electrodacus:

--- Quote from: IanB on September 03, 2021, 12:48:00 am ---In both cases the top surface of the treadmill is moving relative to ground.

--- End quote ---

Seems like a circular discussion.
Maybe I can find some different way to explain thing excluding this part for now.

Say we go back to propeller based vehicle.
Say vehicle speed is 0m/s and wind speed is 0m/s
And say vehicle is 1kg
And you have 10Ws of energy that you can chose to use powering the wheel 90% efficiency or propeller 70% efficiency.
What will you chose to get the vehicle to highest possible speed using the limited available energy of 10Ws ? 
Alex Eisenhut:
You are educated stupid. You are born singular. You need cubic mind. Support Wind Cube or be cursed.
 
Wind Cube only offends the educated stupid.
IanB:

--- Quote from: electrodacus on September 03, 2021, 01:05:32 am ---Say we go back to propeller based vehicle.

--- End quote ---

No, let's not do that. If you keep trying to divert the question and changing the subject, then we will know you are a troll.
electrodacus:
I will make this problem as a reply to all of you and even do the calculation for you just let me know if I'm wrong.

Start conditions:
Wind speed 0m/s
Vehicle speed 0m/s
Vehicle mass 1kg
Available energy 10Ws
Wheel efficiency 90%
Propeller efficiency 70%

So vehicle will end up with 9Ws of Kinetic energy if energy is used to power the wheel and 7Ws if propeller is used.
Thus you probably agree that using wheel for propulsion is best option thus 9Ws is kinetic energy and vehicle is at 4.24m/s

Now at this point with vehicle at 4.24m/s will there be any logic in taking energy from the wheel and putting in to propeller ?
I hope you agree it will make no sense.
Now let say same conditions with vehicle at 4.24m/s but now there is a wind speed of 2m/s in same direction as the vehicle.
Will this change anything ? Will it make sense to take energy from the wheel and power the propeller ?
If your answer is yes please provide the calculation showing that vehicle can increase the current 9Ws kinetic energy using that 2m/s wind.
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