Quote:
Originally Posted by RedDevil
The misconception some people have is that if you have two bodies that are moving relative to one another, that any object that is in touch with both and nothing else cannot move beyond the speed of either.
So we have the ground at standstill, and the wind at a steady pace, and nothing can move against the wind or faster than the wind.
Now if we substitute the wind for a wooden plank, that would mean if you put something in between the ground and the wooden plank and you pusth the plank over that object, it would not move faster than the plank.
Right?
Behold my super simple car:
Note it has a double set of wheels; one in touch with the ground, one in touch with the plank. But the upper set also rests on a disk that is attached to the lower set of wheels, but half its size.
Now if you move the car then the upper wheels will turn at half the speed of the lower wheels and in the opposite direction. As the plank rests on those wheels, it will move in the same direction as the car but at half the speed.
That should be obvious.
Now what happens if you don't push the car, but rather the plank?
Of course the car will shoot away at twice the speed of the plank! Because the plank and car will still move relative to each other with the same ratio as when you push the car.
The wind does not provide as much grip as a wooden plank does, but if your propeller is big enough and other sources of friction are low then it would work just the same. |
1) If the car moves from left to right, the upper wheels will rotate counterclockwise, and the plank will move at half speed in the opposite direction of the car.
2) The video said that the aerodynamic drag of the cars body pushed the car to speed, while momentum of the moving car powered the propeller via the wheel-geared powertrain.
3) Under the law of conservation of energy and the second law of thermodynamics, the propeller can never see as much energy as is contained in the wind.
4) When ground speed and air speed are equal, there is no more momentum impulse acting on the non-propeller parts of the car.
5) There's no additional energy being added to the system.
6) For the car to continue acceleration, would require extracting energy from a negative wind speed to overcome the equilibrium velocity.
7) Perhaps you guys are in possession of an airfoil section that has such a specific lift-to-drag ratio, that it can impart enough thrust to 'tack' on its shaft, lifting beyond some threshold.
8) I'd for one, would still like to see 'proof' that the car did what was said.