Physics brainteaser

Discussion in 'Chit Chat' started by Turok, Nov 10, 2008.

  1. Turok


    Remember the POAT (plane on a treadmill) thread from a year or so ago? Got another one:

    Can a device be built that can travel downwind, faster than the wind, powered only by the wind, steady state?

  2. 151


    Sure, battery powered vehicle with a retractable wind powered generator to charge the batteries.
  3. I believe one of the criteria was powered only by the wind.
  4. It can't go faster than the wind, if its travel direction is exactly down wind (parallel to the wind velocity vector).

    If it is allowed to travel at a down wind angle, then yes. The wind will travel around the curvature of the sail at a faster rate (Bernoulli's) and essentially "pull" the vessel faster than the downwind velocity.
  5. A sailboat. Ice skates.
  6. Turok


  7. Nope. I don't buy it.

    You are imparting energy, through the wheels and into the prop, from the treadmill. That's not wind power. The fact that it goes faster than the treadmill is not important. You have created an energy transfer from the treadmill motor, not the wind.

    Actually blow wind at it, then show it going exactly up wind (or exactly down wind) faster than the wind, with no treadmill. Then patent it!

    Maybe I'm just a born skeptic? :cool:
  8. Arnie


    Your experiment would imply that your little gizmo produces more energy that is uses. But we already that isn't possible. I think what you have done is turn x revolutions of the wheel into x revolutions of the prop. Similar to the leverage of a pully or lever.
  9. Turok


  10. Turok


    It doesn't imply that, and we don't imply that. The device is powered by the relative motion between air and rolling surface. Shut off the 'wind' and the device stops.

    Yes we do.

    #10     Nov 17, 2008