Quote from Turok:
1-Nope -- from the side it was filmed you just couldn't see that there is a long stick holding the streamer out to the *side* (other side from the camera).
2-We certainly agree on this point -- that's the way to prove the point to the average person. To someone knowledgable in physics, the treadmill is the most accurate and controllable way.
JB
1-Yes I know that. It was a trick question to see if you could explain why the streamer, at times, was blowing towards the front of cart, and why the video was cut part way in, right when the streamer was like that.
Look, I understand that a breeze passing through the prop will cause it to spin, which will in turn power the drive wheels, and if the gearing is correct, the cart will briefly be able to go faster than the wind when the wind dips briefly in velocity,since the spinning prop will store a lot of kinetic energy, giving the illusion that it can go DWFTTW, steady state, with a little creative video editing.
The wind is your power source. There MUST be wind blowing through the prop in order to supply power to the drive wheels. As the cart nears wind velocity, there will be no more power source, since the net flow through the prop is zero. This is what is seen in that video. That is why the streamer can be seen, at times, to be blowing towards the front of the cart. The cart is VERY efficient at going down wind, but it cannot go faster than the wind - STEADY STATE - it can only do this for brief periods when the breeze slackens and kinetic energy is powering the cart.
2- I find this an interesting statement, since you didn't recognize the curve ball I threw you with my bike/rollers vs chevy/treadmill comparison. They are not the same experiment. Of course you are correct that you will be slammed into your seatbelts when you slam on the brakes whie on the treadmill - you will be spit off the back.
And once again, the treadmill is not the correct way to demonstrate DWFTTW. The thrust the prop develops is a result of the power input from the wheels. You set it on the treadmill, and once the prop spins fast enough to develop more thrust than is lost due to rolling resistance and power transmission losses, of course it can advance.
I gave you the real way to prove DWFTTW - namely, put the cart in a windtunnel, where the windspeed can be both measured and controlled to maintain steady state, and put the cart on rollers, measuring the distance/speed that the wheels would be covering in the real world. This eliminates the variances in wind speed that are a natural occurence in nature. This would be proof.
----- But since you claim to understand the physics, explain exactly HOW the physics work that enable this. Videos don't cut it.
