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Physics brainteaser
- Thread starter Turok
- Start date
Quote from Haroki:
You're kidding, right?
Nope.
All this is showing, is a device with a very efficient power transmission/prop that can overcome the rolling resistance of the wheels.
Well, as it turns out, the above is also exactly what is needed to go DDWFTTW (directly downwind faster than the wind).
Compared to the street in a tailwind, the treadmill in still air is not "similar", it is not "analogous", it is *identical*.
I'll demonstrate.
Throw the kids in the Chevy and drive down the road at 20mph in a 20mph tailwind.
Roll down the window and stick your hand out -- nothing but still air.
Again check the speedo -- 20mph.
Slam on the brakes ... the kids are thrown forward into their lap belts, the dog hits the back of the seat and the helium filled balloon gets carried all the way to the back of the car (though that's another physics brainteaser entirely)
Now, let's put that same chevy on a long treadmill inside a large garage and shut the door.
Throw the kids in the Chevy and set the treadmill speed to 20mph.
Roll down the window and stick your hand out -- nothing but still air.
Again check the speedo -- 20mph.
Slam on the brakes ... the kids are thrown forward into their lap belts, the dog hits the back of the seat and the helium filled balloon gets carried all the way to the back of the car (though that's another physics brainteaser entirely)
There's no physics difference between the two -- they are identical. In fact, if you were the passenger and were blindfolded, you couldn't tell the difference. Neither can the car, neither can the DWFTTW cart, and neither can any scientific instrument known to man.
If the DDWFTTW advances against the running treadmill, powered only by the air/surface interface, it is truly and absolutely going DDWFTTW.
JB
Quote from Turok:
I have built, and can demonstrate on demand a vehicle which can travel directly downwind, faster than the wind, powered only by the wind, steady state.
http://www.youtube.com/watch?v=Vjt6G8D4x0k
If your device is going faster then the wind ... how would it be possible for it to use the wind for momentum...
dont work... it would be experiencing resistence from the wind its trying to pass
its the equivalent of a bobsled outpacing its pushers.
actually, it is entirely possible for a bobsled to outpace its pushers in the Short-Term, provided the pushers don't hang on
Quote from Turok:
Now, let's put that same chevy on a long treadmill inside a large garage and shut the door.
Throw the kids in the Chevy and set the treadmill speed to 20mph.
Roll down the window and stick your hand out -- nothing but still air.
Again check the speedo -- 20mph.
Slam on the brakes ... the kids are thrown forward into their lap belts, the dog hits the back of the seat and the helium filled balloon gets carried all the way to the back of the car (though that's another physics brainteaser entirely)
JB [/B]
Uhhhh, no.
The kids etc, aren't moving, hence no kinetic energy to throw them anywhere. I know this for a fact cuz back when I was young and skinny, I used to race bikes a little, and would train on rollers during the winter. I could slam on the brakes anytime I wanted and I WOULD NOT go flying over the handle bars.
And really, while you're a good guy, you're delusional if you think it can go DDWWTHDDGVVK or whatever. It IS a neat little device though.
Wanna prove us wrong? Show us a video of this vehicle in a wind tunnel, where the wind speed is known, and show it moving faster than that.
That would fit the scenario you laid out in the OP. What you're missing is that as another poster said, the wind is not the power supply. The wind from the prop is a result of the energy input from the wheels.
They are not the same claim.
I still don't buy it. You are introducing essentially unllimited energy into the system with the treadmill. It doesn't matter how fast or slow it is going.
That treadmill is actually "geared" to the vehicle through the wheels, the pinion gear, and into the shaft and prop. The prop (an "airscrew") then digs thru the air. You have sort of a feedback mechanism, whereby the treadmill pushes against the car, which turns the prop to push back against the treadmill.
That treadmill and its motor are introducing far more energy into the system than simply having wind blow at the car, at the same speed the treadmill is moving.
That treadmill is actually "geared" to the vehicle through the wheels, the pinion gear, and into the shaft and prop. The prop (an "airscrew") then digs thru the air. You have sort of a feedback mechanism, whereby the treadmill pushes against the car, which turns the prop to push back against the treadmill.
That treadmill and its motor are introducing far more energy into the system than simply having wind blow at the car, at the same speed the treadmill is moving.
Quote from Haroki:
Uhhhh, no.
The kids etc, aren't moving, hence no kinetic energy to throw them anywhere. I know this for a fact cuz back when I was young and skinny, I used to race bikes a little, and would train on rollers during the winter. I could slam on the brakes anytime I wanted and I WOULD NOT go flying over the handle bars.
Uhhh yes.
LOL -- your rollers simply don't have enough inertial resistance to throw you over the handlebars. If the earth was as light as your rollers it wouldn't happen in real life either.
Try again on a set of rollers that has a few hundred pound of rotational inertia and tell me the results.
Sorry -- just the facts.
JB
Quote from Wayne Gibbous:
I still don't buy it. You are introducing essentially unllimited energy into the system with the treadmill. It doesn't matter how fast or slow it is going.
That treadmill is actually "geared" to the vehicle through the wheels, the pinion gear, and into the shaft and prop. The prop (an "airscrew") then digs thru the air. You have sort of a feedback mechanism, whereby the treadmill pushes against the car, which turns the prop to push back against the treadmill.
That treadmill and its motor are introducing far more energy into the system than simply having wind blow at the car, at the same speed the treadmill is moving.
Wayne, it's impossible to be "introducing essentially unlimited energy" into the system -- the device can only absorb as much power through the wheels as the prop can push on the air -- which happens to be exactly the same as the wind.
When you put a tension scale between two ropes and pull until you see 10lbs, *both* sides must be pulling 10lbs. It's impossible for one side to pull more than the other, and when in steady state, it's impossible for the wheels and prop not to be resisting each other with equal force.
JB
What I mean by "unlimited energy" is that the treadmill can couple into the vehicle whatever is needed (within limits of the tire-surface friction). This, really, is like having an electric motor actually on the vehicle, with wires leading to a power source. Or instead of the propeller, there was a sliding pully arrangement that traveled along a wire (by grabbing the wire), or a chain and sprocket, etc. The treadmill motor turns the treadmill, which turns the wheels, which pulls the car along the wire. As long as the gearing was correct and the tires didn't slip, the car would easily travel up the wire faster than the treadmill moved. This is not wind power. The prop just offers a loose connection to a non-viscous fluid (air). It's not even needed in this model.Quote from Turok:
Wayne, it's impossible to be "introducing essentially unlimited energy" into the system -- the device can only absorb as much power through the wheels as the prop can push on the air -- which happens to be exactly the same as the wind.
When you put a tension scale between two ropes and pull until you see 10lbs, *both* sides must be pulling 10lbs. It's impossible for one side to pull more than the other, and when in steady state, it's impossible for the wheels and prop not to be resisting each other with equal force.
JB