Direct Downwind Faster Than the Wind #2 (DDWFTTW)

Really this is as simple and as counter-intuitive (at first) as the yo-yo along a table & cotton reel examples.

Basically the cart is being _pushed_ by the wind, and uses the rotation of the wheels to turn a propeller which pushes against the wind even more and allows it to move a little faster than the wind which is pushing it.

Most people seem to assume that they see a windmill (turbine) which powers the wheels.

how about a treadmill video angled to view to the left of it so we can confirm that someone isn't turning a fan on when the cart is placed on the treadmill?

Look at "Downwind Faster than the Wind #7"

Maybe you should stop showing the treadmill "experiment" as if it is equivalent. On the treadmill, energy is coming from the treadmill and being transferred to the propeller which acts in the still air of the room pushing the cart forward. This is a completely different situation than having the cart (with no other power source than the wind) moving at the same speed as the wind. At that critical point the relative speed between the propeller and the wind is 0 mph.

You need to look into the principle of equivalence of inertial reference frames. Galileo, Newton, and Einstein tell us that a cart on a stationary road in a 10 mph tailwind is IDENTICAL to a cart on a road that's moving 10mph under "no" wind.

I don't have access to the equipment so I'd be curious to see the results of placing the cart on a stationary treadmill, then starting the treadmill...

It would probably fall off of the end of the treadmill. It takes a little while for the propeller to speed up enough to provide thrust. Another problem from following their videos and blogging is that if the "wind" is below 2.7 mph this particular design will not work, on the treadmill that means it will just go back until the speed of the treadmill is a least 2.7mph.

Yes, as subductionzone points out, the minimum wind speed for this cart to go faster than the wind is 2.7 mph. Given a long enough treadmill it would backup until the treadmill was going 2.7 mph, and would then start advancing forward.