Down wind faster than the wind

[sol invictus]

Despite visible evidence for C, marginal speed, no kinetic energy, no wind.
They insist that it must be A: the vehicle is at windspeed and not essentially stopped.

LOL, genius

You're really making yourself look like a fool. Energy is not invariant under these transformations.

If you had taken even a first year college course in physics you'd know that energy is the first component of a 4-vector, not a Lorentz invariant. Not that one even needs that - Galilean transformations are enough.

 

[humber]

Keep the $100K, because you're precious. The only winds in this experiment come from you, and the ideas flying over your head.

 

[technoextreme]

And yet WE did.

No you didn't. You in fact rediscovered an 100 year old perpetual motion machine that just happens to ironically be tied to boats. This is the reason why I'm so stubborn because I've seen this before and if it did anything useful we would have found out 100 years ago.

 

[Brian-M]

Well, not necessarily. The gearing works both ways. I'll give you a specific example: if the propeller is geared to move the air backwards (wrt craft) at 2/3 of the wheel speed, the propeller-moved air is moving forward (wrt ground) at 1/3 of the craft speed. The wind will accelerate the craft until the propeller-moved air is moving forward (wrt ground) at the same speed as the wind. But because propeller-moved air is moving at 1/3 craft speed, this means that by this time the craft is moving at 3 times the wind speed.

D'oh!

I worked it out using 1/2 as a convenient ratio. I forgot different ratios would have different limits.

You care whether you understand, and that means you're on the best way to understanding!

I've found the best way to understand a new idea is to work out exactly why your existing ideas are completely, utterly wrong.

 

[ThinAirDesigns]

This is the basis of their claim that the treadmill represents a real wind test.
It can be found at #306

A:
Windspeed 10mph
Vehicle speed 10mph
Difference 0mph

B:
Windspeed 10mph
Vehicle speed 0 mph
Difference 10mph (sign ignored)

Their conclusion: When the difference is 0, the car is at windspeed.

-

Humber, I sure hope folks will go to Post #306 as you referenced it, because it will show that your case "A" and "B" above are NOT the cases that were presented. I have no idea if you simply made a typo error, or if you are intent on twisting the cases, but either way unless you can accurately read words on a page it's garbage in, garbage out.

Here is the ACTUAL representation of case "A" and "B" as copied directly from Post #306:

We are going to mount a wheel driven speedometer and a *chassis mounted* air speed indicator on the device.

Let's just take the case of "as fast as the wind" and compare:

Case "A": cart is going down the street at 10mph in a 10mph tailwind.

Speedometer: 10mph
Air speed indicator: 0mph

Case "B": cart is on the treadmill(TR) which is set at 10mph and is neither moving towards the front of the TR nor to the rear of the TR.

Speedometer: 10mph
Air speed indicator: 0mph

-
Now, if you wish to comment on the above scenario, be my guest. If you wish to disagree with the scenario, that's perfectly OK. BUT if you wish to keep misrepresenting the data in #306 I will continue pasting it in directly so everyone can see the mispresentation first hand.

(as a quick reference for those seeking humbers "mistake", notice that in the #306 case, "A" and "B" always return the same result from the instruments. In humbers "A" and "B" they don't. Now if humbert disagrees with our instrument returns, that's OK --- but humbert should NOT post different data and represent it as "the basis of *our* claim")

JB

 

[humber]

While I can understand how the device works in still air on a treadmill, I'm still trying to see how it works on the ground with a tailwind. My thinking so far is along the lines of:

The wind pushes on the air from the prop, applying a torque to the prop, which through the transmission applies a torque to the wheels to drive the cart along the ground in the direction of the wind.

Is this correct?

But there's no wind. The correct interpretation, is that the cart takes ALL of it's energy from the belt. Hold the cart on the belt, but with the prop de-coupled.
How do you get the prop to turn? Connect it to the wheels. And so it turns.
Due to Newton's law of opposite and equal reaction, the torque on the prop shaft will be the opposite of the wheel drive shaft. These cancel to produce zero torque. That means, the cart will not move, because, there is no torque!
The SOLE purpose of the prop, is to achieve that very condition.
The small travel that you see, is the result of small differences between the two torques, being integrated by the mass of the propeller. Small details, aside, that is all this wonder does.
For yet another time, everybody, the belt drives the cart so that it will stay in place. There is no wind!

ETA: When someone offers you a bizarre alterative, and this is the basis of their faster than wind claims, you might just pay attention to the nature of this forum. Be skeptical.

 

[ThinAirDesigns]

But there's no wind. The correct interpretation, is that the cart takes ALL of it's energy from the belt.
<snip>
For yet another time, everybody, the belt drives the cart so that it will stay in place. There is no wind!

-
Ivor:

While I can understand how the device works in still air on a treadmill, I'm still trying to see how it works on the ground with a tailwind.

-
Ivor, it works *exactly the same in both cases because both "cases" are exactly the same.

There literally isn't a single scientific test (no matter how sensitive the instrument) which can be performed to determine if the air is moving and the ground is still or if the air is still and the ground is moving.

Answer the question "Is a sailboat wind powered or water powered?" and it becomes clear -- "both" or "either" are each correct depending on your frame of reference and neither answer changes how the boat works.

Squeeze a watermellon seed between your fingers and pop it to the other side of the room -- "which finger 'powered' the seed?" Same answer as the sail boat.

Place your two open hands on opposing sides of a empty drinking glass and move your hands in a way that makes the glass spin between them -- "which hand is spinning the glass?". Same answer.

"Which powers the DDWFTTW cart, the road or the wind?" Same answer.

Motion is relative and as long as the rolling surface and the air are moving relative to each other, the DDWFTTW cart will happily zip along.

JB

 

[sol invictus]

How do you get the prop to turn? Connect it to the wheels. And so it turns.
Due to Newton's law of opposite and equal reaction, the torque on the prop shaft will be the opposite of the wheel drive shaft. These cancel to produce zero torque. That means, the cart will not move, because, there is no torque!

So now we're back to the forces always cancel? You already admitted that was wrong, just a few posts back.

 

[humber]

That is precisely, what I said, hence my tautology remark.
You do not read what is posted, but scan it for ammunition or flattery

Quite. We can resort to post-modernist ideas on the nature of reality, or we can look for what we all call EVIDENCE.

The cart has no velocity, no kinetic energy. There is no wind at all.

Which do you think is the most plausible? A call to a Pantheon of deceased physicists, or your own logic and senses, and the highly unlikely prospect that the laws of physics have been overturned by You Tube.

 

[ThinAirDesigns]

The cart has no velocity, no kinetic energy. There is no wind at all.

Relative to where you (or the camera in the video) are standing you are correct -- "the cart has no velocity, no kinetic energy and there is no wind at all"

humbers, I hate to break it to you, but in physics, everything isn't about you.

Relative to the rolling surface -- be it the street or the belt, in both cases the cart HAS velocity, kinetic energy and wind in spades -- exactly the same in both cases as it turns out.

JB

 

[humber]

Edited by Gaspode: 

Removed for breach of Rule 12.

Attack the argument, not the arguer

Replying to this modbox in thread will be off topic  Posted By: Gaspode

 

[JWideman]

what force is moving the cart faster than the wind speed?

The propeller, which is driven by the moving belt.

That's the treadmill. What about the open road?

 

[Brian-M]

Would be theoretically possible to build a device which travels upwind faster than the wind, and would this DUWFTTW cart be practically possible, or would inefficiencies prevent it from working?

 

[Brian-M]

That's the treadmill. What about the open road?

The open road does the same job as the treadmill. Relative to the wind, the open road is moving in the opposite direction, so you end up with the same situation as you have with a treadmill and no wind.

ETA: If the cart is moving at wind speed, then relative to the cart there is no wind, and the road is moving.

 

[ThinAirDesigns]

Me:

Relative to the rolling surface -- be it the street or the belt, in both cases the cart HAS velocity, kinetic energy and wind in spades -- exactly the same in both cases as it turns out.

humbert:

You are an idiot. stop wasting our time.

It's very entertaining to see those two statements adjacent to each other considering that my statement precisely matches tried and true both the physical laws of the universe and their scientific explanations.

JB

 

[ThinAirDesigns]

The open road does the same job as the treadmill. Relative to the wind, the open road is moving in the opposite direction, so you end up with the same situation as you have with a treadmill and no wind.

-

Perfectly put Brian. The evidence to the contrary is not rationally debatable.

Humbert, soon you will be the only one on the forum waving his arms and screaming "they're not the same, they're not the same".


JB

 

[humber]

Your vanity astonishes me. The next time that you are one of your cohorts sarcastically calls someone a "genius" , you might realise, that is perhaps the one thing that can be said to be relative.

 

[Thabiguy]

Would be theoretically possible to build a device which travels upwind faster than the wind, and would this DUWFTTW cart be practically possible, or would inefficiencies prevent it from working?

Sure; just make the propeller blow air backwards wrt cart at, say, 1.5x cart speed (=0.5x cart speed backwards wrt ground). But practically it would be more difficult to build, because unwanted drag will work against you harder when it moves upwind. You would have to put more effort into minimizing losses.

 

[ThinAirDesigns]

Your vanity astonishes me. The next time that you are one of your cohorts sarcastically calls someone a "genius" , you might realise, that is perhaps the one thing that can be said to be relative.

Unfortunately for you, there are many things that are relative -- and the three that are key to this discussion are:

1. Velocity
2. Kinetic energy
3. Wind

There is no absolute (or "real world" as you call it) with any of those three.

JB

 

[sol invictus]

That's the treadmill. What about the open road?

The wind .

I'm not trying to confuse you - the truth is that in all cases the device draws its power from the difference between the velocity of the wind and the velocity of the road.

Think about a sailboat sailing downwind faster than the wind by jibing back and forth really fast. Where is it getting its power from? The answer is that it's exploiting the difference between sea and wind.