Weeble (clockworksaint) wrote,
Weeble
clockworksaint

Question for the physics experts

Is it possible to build a mechanical vehicle, powered solely by the wind, that travels directly downwind faster than the wind? It seems there are some big arguments on the internet over this and some Youtube videos claiming to show such vehicles. Here's one that looks cool, but it's not entirely clear what's keeping it steered onto the road, suggesting that the video might be faked, possibly by just towing the thing:

http://www.youtube.com/watch?v=aJpdWHFqHm0

Here's another video of a little contraption of a similar design that is demonstrating the same feat in a difference frame of reference: rather than travelling faster than the wind over a static ground, it travels against the motion of a treadmill in static air:

http://www.youtube.com/watch?v=1pSYALWQ-nI

Now, whether or not these videos are fake, is such a thing possible? We're not talking about breaking conservation of energy or momentum: there's lots and lots of moving air, so we only need to decelerate some of it to speed up our hypothetical cart. It seems unintuitive, but it's not immediately clear that it should be impossible. Pulleys and levers can seem unintuitive the first time you encounter them.

I'm actually inclined to say it's possible. Am I wrong?
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