Quote:
Originally Posted by aerohead
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.
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related to THE CAR. the plank will move in the same direction as the car related to THE GROUND at half the speed of the car. Just like in Veritasum's video.
The whole point of that demo is to prove that you can make an object move faster than the speed of the two media it interacts with.
Quote:
Originally Posted by aerohead
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.
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I don't know where it says that, but I would agree to it if you replace 'body' with 'propeller'. Als long as the car moves slower than the wind the minimal drag on the body helps a bit though.
Quote:
Originally Posted by aerohead
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.
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Exactly! The car does not break the law of conservation of energy (thermodynamics are not relevant here, but not violated either).
If anything, it makes clever use of it.
There are two media at work here: the wind and the ground.
The wind pushes against the propeller, the ground pushes against the wheels.
The forward force on the propeller and the wheels are roughly equal.
But the distance the wheels move over the ground is larger than the distance the propeller moves the air relative to the car. And energy is force times distance.
So the energy needed to spin the propeller to withstand that force is less than the energy obtained by pushing the wheels over the ground with that same force. No broken laws, just a well used one.
Quote:
Originally Posted by aerohead
4) When ground speed and air speed are equal, there is no more momentum impulse acting on the non-propeller parts of the car.
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Ground speed and air speed are equal in a windstill. The car obviously has no power source then. I think you meant to say something else, but I'm not guessing.
Quote:
Originally Posted by aerohead
5) There's no additional energy being added to the system.
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Indeed.
Quote:
Originally Posted by aerohead
6) For the car to continue acceleration, would require extracting energy from a negative wind speed to overcome the equilibrium velocity.
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Negative to the car you mean? Because that is exactly what we try to achieve.
There's no such thing as negative wind speed compared to the ground.
There's no such thing as negative wind speed compared to the surface of the propeller blades.
Obviously the wind needs to keep pushing against the propeller. It has to turn to allow for that.
Again, energy is force
times distance. And as the propeller is forcing the air backwards slower than the wheels move over the ground, it needs less energy to do so than the wheels provide from the same force.
Quote:
Originally Posted by aerohead
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.
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No need for tacking if you rotate around an axle for an 'infinite tack'. The propeller is nothing but two sails on an axle.
As for
lift to drag ratio, that can go all the way to 60:1. Seems adequate.
Quote:
Originally Posted by aerohead
8) I'd for one, would still like to see 'proof' that the car did what was said.
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Ha! What would anyone have to do to convince you?
When building the damn thing, having sceptics inspect it, having an official registration of a record 2.8 times wind speed and all, and winning a 10,000 dollar bet with an UCLA professor does not even convince you?
No proof will ever be good enough for you, because the only thing you'd do with it is trying to debunk it.
Because deep in your heart you KNOW it cannot work.
Because you make a mistake in interpreting its physics, but you cannot admit that somehow.