[Bored chemist]

If the average speed was faster than the wind that would violate conservation laws,

Nope.

[Bored chemist]

If there was a perfectly steady wind over a level course that is say a kilometer in length the vehicle will certainly...

Your "certainty" seems unfounded.
Could you please explain in detail where my idea fails?

[Origin]

Nope

I 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?

[Bored chemist]

Nope

I 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?

That's an understandable mistake to make.
Here's where I made it.


https://www.thenakedscientists.com/forum/index.php?topic=82462.msg643362#msg643362

And here is where I changed my mind (and why)

https://www.thenakedscientists.com/forum/index.php?topic=82462.msg643539#msg643539

[Origin]

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.  Since the generator and the motor are not 100% efficient (the propeller is not 100% efficient either) I do not think that you will be able to even make it back up to your speed before you lowered the wheel.

[Halc]

That wheel on the ground will be a big drag and slow you down considerably.

No, it's a relatively small drag.  Compute the work done by the wheels to the work done by the prop. In equilibrium, force is the same in both cases, so it's a matter of difference in distance.  It might be a 3-1 ratio at slower speeds, and efficiency lost between prop and wheels isn't that bad.

[Bored chemist]

That wheel on the ground will be a big drag and slow you down considerably. 

The whole windward surface of the balloon is being pushed by the wind, that's doing nearly all the work of moving the balloon WRT the ground.
The load from the wheel on a stick is small by comparison.

[hamdani yusuf (OP)]

Update on the wager.
https://twitter.com/veritasium/status/1405699594013470723


He even shows a clear close-up image of the exposed gear assembly. It shows that the whole system is purely mechanical.



His transparency brings credibility.
The ratio of the gears seems to be 1:1
So the speed multiplier must come from wheels radii vs blades radii, and also blades angle.

[hamdani yusuf (OP)]

That's an understandable mistake to make.
Here's where I made it.


https://www.thenakedscientists.com/forum/index.php?topic=82462.msg643362#msg643362

And here is where I changed my mind (and why)

https://www.thenakedscientists.com/forum/index.php?topic=82462.msg643539#msg643539

Wise Quotes. When an honest man discovers he is mistaken, he will either cease being mistaken, or he will cease being honest.

I'd like to express my respect to your scientific integrity. We all make mistakes sometimes. How we response when we discover one will show who we are.

Albert Einstein Quotes ... A person who never made a mistake never tried anything new.

[hamdani yusuf (OP)]

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.

They say that a picture speaks a thousand word. So here we are.

- belt velocity is 1 m/s.
- no slip between belt and wheels.
- front (right side) wheels turn independently, and installed for balance only.
- rear wheels are coupled using a V-belt.
Since everything is balanced, the speed of the car is 0.

[hamdani yusuf (OP)]

Now replace the pulley of the top rear wheel with a bigger one, e.g. three times bigger.

It would make the rear top wheel rotates slower than the others. So we need to replace the wheel with a slippery type.
This will enable the car to get a push from the top conveyor, hence accelerates to the right. Acceleration stops when the rear top wheel has the same tip speed as the top conveyor.

[Origin]

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

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. 

[hamdani yusuf (OP)]

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? Remember that the bright grey wheel is slipping. It doesn't have a problem to spin at different tip speed than 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.

[Halc]

Why not?

OK, I read you wrong. You said this:

Acceleration stops when the rear top wheel has the same tip speed as the top conveyor.

You're saying that acceleration stops when the wheel stops slipping, but I took it as when the wheel moves at the conveyor speed.
I agree. My bit about getting the car to move faster than either conveyor still stands. Like the real car, it is powered by the different speeds of the medium against which the forces are applied.

[hamdani yusuf (OP)]

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.

In real life experiment, the starting condition is not symmetrical. The bottom wheels don't spin and the car moves along with bottom conveyor. The bright wheel doesn't spin since it's locked by the V-belt. Top dark wheel spins at 2m/s, which is the speed difference between top and bottom conveyors. Once the brake is released, the bright wheel starts to spin due to friction. It turns the bottom wheel to turn 3x as fast. It makes the car to accelerate to the right until the tip spin of the bright wheel equals top conveyor. When the force of internal friction in the car mechanism is non-zero, the bright wheel will spin at lower speed, hence generate balancing force from friction with top conveyor.

[hamdani yusuf (OP)]

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.

They don't care about average speed, since it would take initial speed into account, which is 0.
They care about terminal speed, where total acceleration is 0. It occurs when the total force pushing the car forward is balanced by friction in car mechanism.

[hamdani yusuf (OP)]

In real life experiment, the starting condition is not symmetrical.

This asymmetry skews our perspectives in analyzing the problem. We have been accustomed to see various phenomena from earth perspective. In many cases it's fine, but in some other cases it gives us false assumptions which lead to unexpected results.   
If we see the motions of planets from earth perspective, they don't seem to make sense. Similar thing might have happened in this case.

[hamdani yusuf (OP)]

My bit about getting the car to move faster than either conveyor still stands.

What does it mean? Do you still believe that to go faster than top conveyor, the car needs additional power source?

[hamdani yusuf (OP)]

Ernest Rutherford Quote: “All of physics is either impossible or trivial. It is impossible until you understand it, and then it becomes trivial.”
Once you understand the problem, it becomes trivial. In retrospect, we might think that it's too trivial to worth $10k.

[hamdani yusuf (OP)]

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.

There is no figure-8 in my picture. When the size of the pulleys are equal, we get back to my previous picture. Tip speed of bottom wheels are 1 m/s. The car would be stationary wrt observer, or 1 m/s relative to bottom conveyor.
With 2:1 ratio, the car would move 2 m/s relative to bottom conveyor, or 0 m/s relative to top conveyor.
With 3:1 ratio, the car would move 3 m/s relative to bottom conveyor, or 1 m/s relative to top conveyor.
When the ratio is negative, like in 8 figure V-belt, the car would move backward.
Note: don't worry about the right dark wheels. Their solely function is to prevent the car from tumbling.