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If the average speed was faster than the wind that would violate conservation laws,
If there was a perfectly steady wind over a level course that is say a kilometer in length the vehicle will certainly...
Nope
Quote from: Bored chemist on 17/06/2021 18:24:24NopeI could certainly be wrong. My simple minded way of looking at this is; if the vehicle is powered by air movement and on average the relative air movement is 0 fps or negative fps, where is the force coming from to maintain the movement?
I can lean out of the basket and put the wheel in contact with the ground so it spins the generator and creates electricity.I can use that electricity to run a motor and have that drive a propeller and I can use that to move my balloon through the air in any direction I choose.
That wheel on the ground will be a big drag and slow you down considerably.
That's an understandable mistake to make.Here's where I made it.https://www.thenakedscientists.com/forum/index.php?topic=82462.msg643362#msg643362And here is where I changed my mind (and why)https://www.thenakedscientists.com/forum/index.php?topic=82462.msg643539#msg643539
The vehicle collects energy by reducing relative velocity between earth surface and the air. It would be easier if the analysis is done in a reference frame where the total momentum of interacting system is 0. Conservation of momentum guarantees that observers staying in this frame doesn't change their velocity due to the interaction.The fact that the vehicle only interacts with a small part of the wind adds the complexity of the problem. So, to simplify the system, we can replace the salt lake bed with a conveyor on the floor moving to the left. The wind is replaced by a conveyor hung on the ceiling, moving to the right. The vehicle starts at the same velocity as bottom conveyor.
If the average speed was faster than the wind that would violate conservation laws, clearly if there is no force from the wind (because you are moving faster than the wind) why would you continue to maintain speed? It is nonsensical
If the top wheel has the same tip speed as the top conveyor, it wouldn't rotate at all, but then the bottom wheel shouldn't.
Why not?
Acceleration stops when the rear top wheel has the same tip speed as the top conveyor.
Let's start with the car stationary to the frame of the conveyors. Dark wheels all spin at 1 m/s since they don't slip. The pulleys and V-belt will force the bright wheel to spin at lower tip speed, i. e. 1/3 m/s. It's possible since it is slipping. But as long as it's not perfectly slippery, there would be some friction forcing the bright wheel to increase its tip speed. This force is transmitted through pulleys and V-belt to bottom rear wheel, increasing its tip speed too. This will make the car move to the right, since the front wheels can spin independently.
I looked at wiki and some other sources and no where did is see that the average speed of the vehicle over the run was faster than the speed of the wind. I only saw that the speed of the vehicle could exceed the speed of the wind at some point.
In real life experiment, the starting condition is not symmetrical.
My bit about getting the car to move faster than either conveyor still stands.
So how do you get it to go faster than the top conveyor? Simple: Loop the belt in figure-8 around the unequal size pulleys. The closer in size the pulleys are, the faster it goes.