Down wind faster than the wind

[Brian-M]

If anyone's interested, here are the images Humber linked to a while ago. I've resized them, cropped them and indexed them to get the file size down to something manageable. While I was at it, I also added my own comments at the end in red.

BTW:

Humber, looking at the last of your posts I responded to, I think I'm getting an idea why you (incorrectly) believe you would have wind resistance while travelling at wind speed.

Are you thinking of wind speed as the average velocity of the air molecules, using their scalar values?

Wind speed is the average motion of the air molecules. You can only get that from their velocities by using vector values.

For example, draw some dots on a frisbee, and throw it.

The dots will not only be travelling forwards with the frisbee, but they'll be moveing side to side as the frisbee spins. As such, the average velocity of the dots will be much higher than the velocity of the frisbee.

If you use the vector values of the dots' velocity, the side-to-side motion cancels out, and the average motion of the dots is exactly the same as the frisbee-speed.

Wind speed is the average motion of the air molecules, not the average velocity.

 

[spork]

Humber...

If you want to convince me the DDWFTTW device won't work, you will have to either show that the animated cart pictured won't move at twice the speed of the converyor belt in the same direction as the conveyor belt...

I'd like to make two predictions at this point:

1) Humber will easily be able to explain why your cart won't work as you say.
2) Most of us could easily build and demostrate your cart doing exactly what you say.

We must not attempt to change the nature of the universe. You guys are playing with fire. If this results in a black-hole and the earth is instantly swallowed up - don't come whining to me

 

[Scazon]

The dots will not only be travelling forwards with the frisbee, but they'll be moveing side to side as the frisbee spins. As such, the average velocity of the dots will be much higher than the velocity of the frisbee.

Speed- velocity is a vector. If the dots' velocity were to be higher than that of the frisbee, there would be a little cloud of dots moving away in front of it, which is a pretty picture.

 

[Michael C]

Here is a simple physics question from the YoyoDyne Propulsion Systems employment exam:

[qimg]http://www.internationalskeptics.com/forums/imagehosting/thum_15144492613dfb1b89.jpg[/qimg]

If the parachute is moving downwind at 3 smoots pre microfortnight, how fast and in what direction is the yo-yo moving?

3R2/R1 smoots pre microfortnight, in the direction of the wind.

Thanks, Dan O, for that very clear demonstration. I should add that this is nothing other than Martin Gardner's spool that moves backwards that I already mentioned. I just didn't have your neat idea of attaching the parachute!

 

[humber]

Don't lie - it makes it even worse.

That restriction would leave you speechless
However, the list is getting shorter, and the exemptions rising.

Keep repeating falsehoods, they remain false. It is supported by every piece of empirical data ever collected. It's your ignorant and uninformed opinion against every physics book, published and on the web, every physicist, every layperson with even a passing familiarity with physics. Are you really that arrogant?

"It is supported by every piece of empirical data ever collected."

Pleas show the data that supports the idea that the treadmill is the equivalent of a windtunnel.

Please transform f=ma to your new viewpoint.

Again you illustrate your utter lack of comprehension. Something on a treadmill is not "always moving at windspeed". It's moving at wind speed if it's at rest with respect to the air. For a treadmill in a closed environment that means at rest with respect to the room/van/planet/whatever the treadmill is sitting on. If it's moving with the treadmill belt, for example, it's equivalent to something at rest on the ground in a steady wind.

[/QUOTE]

"It's moving at wind speed if it's at rest with respect to the air

Which air are you talking about today?

"For a treadmill in a closed environment that means at rest with respect to the room/van/planet/whatever the treadmill is sitting on"

You agree. It shows windspeed independently of the environment

 

[humber]

Are you going to address Myriad's chain-driven device a few posts above? That's the cleanest I've seen yet, and it's obvious how it will move. Do you agree it will go down chain faster than chain-speed?

If so, why are you still arguing?

And if not, why not?

Perhaps later, but for now, let's talk about your cart and treadmill

 

[humber]

Yes they do. They both have the same velocity with respect to the surface before, during, and after stopping, and they both have the same mass, therefore they both have the same kinetic energy with respect to the surface before, during, and after stopping. You are still making the mistake of thinking that kinetic energy is not relative.

They have the same velocities, or not.

The charge in the battery is an analog of the vehicle's kinetic energy.
The difference in charge may differ by an arbitrary amount, not related to mass. So they are not equivalent.

 

[humber]

OK, so you want to abandon the simple analogy that illustrates the point perfectly in favour of a much more complicated one?

No, a more complete one

If they momentarily strike you, transferring some of their momentum to you, then they have pushed you. If a ball in front to you is going slower than you it will do the same, pushing you back. I'm using 'push' instead of 'transfer of momentum from collision' for simplicity.

Note: The momentum which they must pick up from somewhere else comes from the other balls/air molecules. When you use a sail to accelerate in the wind, you are slowing down the wind, by a very, very, tiny amount.

That simplicity destroys the model. The collisions are not all directly ahead, or in front. Very tiny amount, but only becasuse of the large scale. I am talking not about that, but an analogy with a small object moving through
a fluid medium.

Assuming this is random action...
If you are travelling in the same average direction the sideways collisions will cancel out exactly, with the same result as if there were no sideways collisions.

It can't said to be random if you force a condition. The point is that the collisions are random.

When you travelling at average velocity, all collisions will average out exactly, giving the same result as if there were no collisions.

When you are travelling at below average velocity, the collisions from behind will exceed the collisions from ahead, pushing you forward.

It requires no energy to travel at windspeed. A bubble or balloon can do it with ease. It always requires energy to travel at less than windspeed. If you are simply standing on the ground, you are using the earth's kinetic energy to travel at less than windspeed, reducing the earth's kinetic energy, relative to the wind.

Well that then becomes the "average" velocity. That is not denied, but that some of the energy will be lost due to the constant and random collisions along the way, and that limits the velocity. The only energy available is in the immediate surrounds, not from the wind "back there"

You haven't got a clue what you're talking about. The heat from electrical current is caused by the energy exerted in order to pass through the material. Collisions from electrons bouncing off each-other do not produce waste energy. Electrons still do all this when passing through a superconducter, but no heat is generated because no energy is required to pass through the material.

The charges are moving in an electrical field. If I make the analogy another mechanical system, then that would add nothing.
It was to show that "particles" do not travel in ordered queues, but follow
a much longer path, and energy is lost upon the way.
Superconductors have low resistance, because they do travel synchronously.

Ok, if you don't want a treadmill, to set asside the differences in the relative velocity of the ground, we'll assume the person doesn't hit the ground, but remains stuck on the bonnet of the car.

Ok, let's say the person is on a skateboard and hits a car (or is hit by a car) at 60mph.

If a skateboarder is travelling at 60 mph and hits a stationary car, he is decellerated by 60 mph.

If a skateboarder is stationary, and is hit by a car travelling 60 mph, he is acellerated backwards to 60 mph.

Decellerating 60 mph is exactly the same thing as acellerating backwards to 60 mph.

The formula for kinetic energy is: E=1/2M(V^2)

That's the total accumulated, not the formula for the exchange over time.

In both cases the change of velocity is the same, and the velocity is the same (and the injuries are the same). The kinetic energy transferred is exactly the same in both cases.
There is no difference.

I did say that the person could be a mass, but the injuries will not be the same. In one case, the only energy available to do harm is the kinetic energy of the person, in the latter, that of the car.

The amount transferred, also depends upon the contact time.

That will change, but also, in one case, the smaller body comes to rest, and in the other not. The final velocities, perhaps even continuously, are not the same. It is certainly possible to differentiate between the two.
A third observer, common to the car and the person would certainly agree, as would the person.

 

[humber]

If anyone's interested, here are the images Humber linked to a while ago. I've resized them, cropped them and indexed them to get the file size down to something manageable. While I was at it, I also added my own comments at the end in red.

Thanks, Brian-M

[qimg]http://www.deadsquirrel.net/images/humber-cart.gif[/qimg]

[qimg]http://www.deadsquirrel.net/images/humber-friction.gif[/qimg]

BTW:

Humber, looking at the last of your posts I responded to, I think I'm getting an idea why you (incorrectly) believe you would have wind resistance while travelling at wind speed.

Are you thinking of wind speed as the average velocity of the air molecules, using their scalar values?

Wind speed is the average motion of the air molecules. You can only get that from their velocities by using vector values.

For example, draw some dots on a frisbee, and throw it.

The dots will not only be travelling forwards with the frisbee, but they'll be moveing side to side as the frisbee spins. As such, the average velocity of the dots will be much higher than the velocity of the frisbee.

If you use the vector values of the dots' velocity, the side-to-side motion cancels out, and the average motion of the dots is exactly the same as the frisbee-speed.

Wind speed is the average motion of the air molecules, not the average velocity.

The difference is not important. Of course, they are vectors, but if random, then you have no information about each collision, but only a probability of its occurrence. To do this would be to stray off the point. The ideas are not analogies but metaphors. If you want a fully detailed explanation, then there are plenty of sources. Why not do that then? Take a look at some basic fluid theory?

But frisbees face the same problem. The drag is always there, otherwise all objects could reach windspeed. Of course they do not, because the force driving the object, is met my another, as the result of moving through the medium. That is drag. Putting your finger in a downstream flow of water does not generate a path to the river bed, upon which you may walk. It comes in all sides, to fill the gap. Air is subject to gravity, there is pressure. Wind is lower pressure air, because it has a higher average velocity realative to the surrounding air. Therefore, when you say "downwind" you are really breaking down your own argument. I can be with the wind or against it, if I change my reference, no? It's not direction, but "through".

 

[humber]

That's pure genius. This keeps getting better and better....

humber???

Naturally, non of these devices can exhibit power gain, and so are of limited use.They are one form of gearing or another, with the force closer to the centre of mass or not, and play with the ratio of rolling to static friction, to the delight of those easily amused.

 

[humber]

Here's my visual depiction... although it doesn't even come close to the simple elegance of the image Dan O presented, it does have the advantage of working in the same way as the DDWFTTW device in the OP does. (Only with a wheel pushing/pushed by a conveyor belt, instead of a propeller pushing/pushed by the wind.

Humber...

If you want to convince me the DDWFTTW device won't work, you will have to either show that the animated cart pictured won't move at twice the speed of the converyor belt in the same direction as the conveyor belt, or explain why using a propeller with the wind is different from using a wheel with a belt.

[qimg]http://www.deadsquirrel.net/images/brians-cart.gif[/qimg]

Brian-M,
There is no limit to the number of machines that can be designed if you don't take in to account the energy budget. See Ynot's ironic response.
A hypthetical vehicle can do anything.
If you do want to convince me, then some calculations would be handy, to show that you hav conserved energy and momentum, for example.

 

[humber]

I'd like to make two predictions at this point:

1) Humber will easily be able to explain why your cart won't work as you say.
2) Most of us could easily build and demostrate your cart doing exactly what you say.

We must not attempt to change the nature of the universe. You guys are playing with fire. If this results in a black-hole and the earth is instantly swallowed up - don't come whining to me

Forsooth. sayeth The Spork

 

[ynot]

Despite what I said in my last post the sceptic inside still has some unanswered questions and I must retract my acceptance of the claim that a vehicle can travel downwind faster than the wind solely in the direction of the wind.

The two main issues are . . .

Can the thrust if the propeller ever exceed the rolling resistance caused to create that thrust? I don’t see how it ever can. If it could the vehicle would be able to be self propelled by it’s own inertia. When the vehicle has reached the speed of the wind or is placed on the treadmill in no wind, then wind can’t be considered as a factor as there simply isn‘t any wind relative to the vehicle. When the vehicle is placed on the treadmill the thrust of the propeller is created solely by the motion of moving treadmill surface relative to the vehicle, and is being transferred to the propeller via the turning wheels and linkages. This is not free energy and there has to be a rolling resistance energy loss that is greater then the energy of the thrust developed by the propeller.

The second issue is whether two opposing winds have a compounding effect or whether they somehow cancel each other out. The wind is moving relative to the ground at 10mph and the vehicle is travelling with the wind at 10mph. It’s claimed that some of the speed of the vehicle is coming from the thrust of the propeller. If say 3mph of the vehicles speed is coming from the propeller then only 7mph of speed is coming from the 10mph wind. What happens to the remaining 3mph of wind? As the vehicle is travelling at the speed of the wind it can’t be going past the vehicle at 3mph.

If there’s something I’m missing what is it?

 

[humber]

Thanks, Brian-M

[qimg]http://www.deadsquirrel.net/images/humber-cart.gif[/qimg]

[qimg]http://www.deadsquirrel.net/images/humber-friction.gif[/qimg]

BTW:

I haven't "forgotten the wind", Brain-M, but shown that is is not necessary to the operation. If shown to you, what would make you think this device to have anything to do with windspeed?

I am saying the device works in still air, because it can. The "parachute" is a drag generator, and drag increases with velocity. In practice, the prop generates the drag, so the velocity refers to the speed of the prop. It is only necessary to ensure that the drag can be varied (in some way) by the connecting shaft.

The gearbox can be anything that you like, all that has to happen is that the forces applied to each shaft are the same, and therefore equal and opposite. The velocity of each shaft is not that important. All the driving force comes from the belt.

If the prop is loaded, say with the finger, then it will perhaps be slowed, reducing the drag produced. The cart would then begin to move backwards, but the force driving the prop, comes from the belt via the wheels, so whatever the prop does, the wheels do the opposite. so restoring the balance.
It is an automatic and natural system, that ensures balance.
The cart is not moving, so the forces upon it must be in balance (the small movement is due to imperfections in that balance). The process is constrained by the friction available between the wheels and the belt.

The balance occurs because the driving force of the prop, and the wheels are from the same source. If the drag created by the prop is replaced with something that generates a retarding force that does not need air, then the device would work in a vacuum.

I am not saying it is "like" anything. I am saying that the treadmill works as I have described.

The Galilean theory that accompanies the treadmill, is simply an ad hoc creation to justify replacing "beltspeed" with "windspeed".

Be aware, that there is no evidence that the real cart can do much at all except to be blown by the wind.

Requests for demonstrations that would serve to confirm that the treadmill is just a force balance, and operates differently from that claimed, have been denied.

I refer to the the inclined plane tests, for example.

Suddenly, the publicity seekers, and their reliance upon video evidence, no longer seem so keen to show us proof.

The treadmill is critical support for the cart - it is the eye-catching demonstration - but it is a deception to relate this simple force balance to the cart's actual performance.

 

[sol invictus]

"It is supported by every piece of empirical data ever collected."

Pleas show the data that supports the idea that the treadmill is the equivalent of a windtunnel.

Oh, we could start with all the data ever collected on particle physics. Then there's all the data on electromagnetism, mechanics, and gravity. Every known equation and law of physics is invariant under changes in inertial reference frames, and all that data supports the known laws.

Please transform f=ma to your new viewpoint.

Oooooh - that's going to be really hard. It's going to be veeery complicated....

wait for it....

are you ready?


Are you sure?


F=ma

"It's moving at wind speed if it's at rest with respect to the air

Which air are you talking about today?

The air around the vehicle.

Naturally, non of these devices can exhibit power gain, and so are of limited use.They are one form of gearing or another, with the force closer to the centre of mass or not, and play with the ratio of rolling to static friction, to the delight of those easily amused.

Does it or does it not move downwind faster than the wind? Yes or no?

 

[sol invictus]

"It is supported by every piece of empirical data ever collected."

Pleas show the data that supports the idea that the treadmill is the equivalent of a windtunnel.

Oh, we could start with all the data ever collected on particle physics. Then there's all the data on electromagnetism, mechanics, and gravity. Every known equation and law of physics is invariant under changes in inertial reference frames, and all that data supports the known laws.

Please transform f=ma to your new viewpoint.

Oooooh - that's going to be really hard. It's going to be veeery complicated....

OK, here it is:

F=ma

"It's moving at wind speed if it's at rest with respect to the air

Which air are you talking about today?

The air around the vehicle.

Naturally, non of these devices can exhibit power gain, and so are of limited use.They are one form of gearing or another, with the force closer to the centre of mass or not, and play with the ratio of rolling to static friction, to the delight of those easily amused.

Does it or does it not move downwind faster than the wind? Yes or no?

 

[Michael C]

Naturally, non of these devices can exhibit power gain, and so are of limited use.They are one form of gearing or another, with the force closer to the centre of mass or not, and play with the ratio of rolling to static friction, to the delight of those easily amused.

Spork's vehicle doesn't exhibit power gain, nor did he claim that it does. It can indeed be compared to a form of gearing, where increase in speed is traded for decrease in traction.

Dan O's device is certainly an amusing toy, but that's not the point. The question is: does the yo-yo move faster than the parachute, or not?

 

[humber]

Oh, we could start with all the data ever collected on particle physics. Then there's all the data on electromagnetism, mechanics, and gravity. Every known equation and law of physics is invariant under changes in inertial reference frames, and all that data supports the known laws.

There you go a again...but not all grey things are elephants.

Not one of them will support your contention that the treadmill is a windtunnel

Oooooh - that's going to be really hard. It's going to be veeery complicated....

wait for it....

are you ready?


Are you sure?



F=ma

Good, but I do first have to check, you know.

Now please provide the tensors that link your "frame of reference" to that of the grounded observer. The belt can serve as an exemplar.

[/QUOTE]

The air around the vehicle.

The still air, then

Does it or does it not move downwind faster than the wind? Yes or no?

What you don't appreciate, is that there is no problem going beyond windspeed. A car can do this, no?

So what's the difference? Self-powering. Include the energies required and expended, and then I will take a look. Patent office full of such devices, that don't work for the above reason.

Hey, guess what? Otherwise they would!

 

[sol invictus]

There you go a again...but not all grey things are elephants.

They're the laws of physics, humber. They're called that for a reason - because they apply to everything, all the time.

Not one of them will support your contention that the treadmill is a windtunnel

Every single physics text agrees with me and disagrees with you. Good luck with that.

Now please provide the tensors that link your "frame of reference" to that of the grounded observer. The belt can serve as an exemplar.

You don't know what a tensor is, humber. What links the two frames is a trivial Galilean transformation: t'=t, x' = x + vw t, y'=y, z'=z, where vw is the velocity of the wind (which I've taken to be in the x-direction).

What you don't appreciate, is that there is no problem going beyond windspeed. A car can do this, no?

So what's the difference? Self-powering. Include the energies required and expended, and then I will take a look.

What are you talking about? Both Myriad's and dan O's devices are powered by the chain/wind (or more precisely by the relative motion of the chain/wind and the ground), just like the cart.

Does the spool move faster than the wind? Does Myriad's wheel roll faster than the chain speed?

Yes or no, humber?

 

[humber]

Spork's vehicle doesn't exhibit power gain, nor did he claim that it does. It can indeed be compared to a form of gearing, where increase in speed is traded for decrease in traction.

Dan O's device is certainly an amusing toy, but that's not the point. The question is: does the yo-yo move faster than the parachute, or not?

What is the relevance Michael_C? To the topic at hand?

That problem is not mathematical but one of perception. You are supposed to be "surprised" at the result. Like the treadmill. "oooh it's going up hill"
If you like, I can post some similar sophisms from a book that I have, all of them along the same lines.

More sleight of hand to make you think that in that "native" way. You know it has no power gain, so it can be dismissed as unworthy of exploration.