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Mess with your minds: A wind powered craft going faster than a tail wind speed.

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electrodacus:

--- Quote from: IanB on September 01, 2021, 05:35:43 am ---
--- Quote from: electrodacus on September 01, 2021, 05:21:50 am ---The rug is pulled at constant speed and I'm siting on it and I can just relax. On a treadmill at constant speed I still need to burn plenty of calories.
--- End quote ---
Here is someone standing on a treadmill, feeling very relaxed, and not burning any calories:

https://youtu.be/GvfF4TeXz7U


--- Quote ---There are no weird scenarios is just you (most of you) (all of us) not able to understand there is a big difference between a treadmill and that rug.
--- End quote ---
There, fixed that for you.

--- End quote ---

Yes that is a very long treadmill so he has some time but not as much as me on a rug.
The thing is that he is not driving the opposite way on the long treadmill as the vehicle in my diagram will need to in order to not move from right to left.
Is all of you here there are sure other people capable of understanding what I'm saying.
But feel free to run the experiment as in my diagram and if you can prove me wrong (vehicle driving from left to right) then I will pay for your expenses in making that experiment.

I have no better way to explain the difference between a treadmill and a rug or piece of paper that moves relative to the ground other than the ones I mentioned before.  If I think of something better I will make sure to let you know but for you the most convincing will be to do your own experiment and see that you can not get the result you expect or want meaning you can not make the vehicle moving from left to right. 

Kleinstein:
The difference between the belt of the treadmill and the piece of paper pulled is that the belt is going around and reused from time to time.
However for the sake of the experiments there is no relevant difference: both present a moving (driven by an external) surface.

Would it make a different if the paper is pulled by a motor (e.g. wind up a roll of toillet paper) and not a human ?

cbutlera:
Much earlier in the thread you talked about aphantasia and you gave a detailed description of your mental image of air.


--- Quote from: electrodacus on August 25, 2021, 10:08:05 pm ---The way peoples brain work is very different likely way more different than you imagine.  You should search about Aphantaisia that affects maybe 1 to 3% of the population the others have a spectrum of capabilities in creating a mental image. And you should also look-up "Internal monologue" where an estimated 30% of the population has no internal monologue.  You will be blown away.
I can create a mental image (sort of average) and I sure have an internal monologue so I think more abstract using language.
I can simulate fairly accurately in my head how a simple cart like those in my diagram will work including what wheel is the generator and witch is the motor and I can know the outcome.
I can also imagine air as a multitude of small particles moving at a relatively constant speed above the ground and that have elastic forces keeping them apart like repelling magnets and then imagine a vehicle driving in the same direction at higher speed than this air molecules and can see that air molecules can no longer help accelerate the vehicle (impossible) but I can also imagine this now higher pressure behind the vehicle meaning higher density (more air particle in the same volume now with higher forces keeping them apart same as force increases when you try to bring two opposing magnets closer).
This is the so called stored energy and as vehicle continues to accelerate this pressure will reduce meaning the density of air molecules drops up to the point that there is not enough pressure to cover the vehicle losses and so vehicle will start to decelerate until it will get below wind speed.
If this description created for you a mental image (visualizing this moving animation) then you will also know vehicle can not be powered by wind when vehicle speed is higher than wind speed in the same direction.

--- End quote ---

With this mental model of air, what you have been saying about energy storage, and other characteristics of gases, would make some sense.

Unfortunately this is a very poor model for air, or any other gas.  For example, the particles in your model appear to only be moving at the speed of the wind, so it is very easy for a vehicle to outrun them.  In reality, the molecules of nitrogen, oxygen and other gases that make up the air, are moving randomly and at speeds comparable to and often higher than the speed of sound.  There are also no significant forces between the molecules keeping them apart, except briefly when they collide with one another or with other objects.

A far better model is that used in the kinetic theory of gases.  The Wikipedia page on this subject includes an animation that may help you to form a much more useful mental image. https://en.wikipedia.org/wiki/Kinetic_theory_of_gases  Once you have moved over to using that model, a lot of the things that others on this thread have said should begin to make sense.

I think that your other sources of disagreement with the rest of us may be due to poorly defined frames of reference.  In particular, the wrong choice of reference frame can obscure the simple relationships between force, distance and energy or work done.  I tried to explore this earlier with my thought experiment with a passenger walking down the aisle of an aircraft.

I have aphantasia myself, so I do have some sympathy with you.  I can't form any kind of internal visual images, but I can form what I can best describe as invisible wire-frame images, that I can freely manipulate and rotate.  I can't see them in any visual sense, but I can sense them.

armandine2:
mechanical systems are familiar and knowledge of them is often taken for granted - I think you'd be less likely to do so for their electrical or chemical equivalents.

... mechanical paradoxes seem though accessible challenges to us:

electrodacus:

--- Quote from: cbutlera on September 01, 2021, 10:46:13 am ---With this mental model of air, what you have been saying about energy storage, and other characteristics of gases, would make some sense.

Unfortunately this is a very poor model for air, or any other gas.  For example, the particles in your model appear to only be moving at the speed of the wind, so it is very easy for a vehicle to outrun them.  In reality, the molecules of nitrogen, oxygen and other gases that make up the air, are moving randomly and at speeds comparable to and often higher than the speed of sound.  There are also no significant forces between the molecules keeping them apart, except briefly when they collide with one another or with other objects.

A far better model is that used in the kinetic theory of gases.  The Wikipedia page on this subject includes an animation that may help you to form a much more useful mental image. https://en.wikipedia.org/wiki/Kinetic_theory_of_gases  Once you have moved over to using that model, a lot of the things that others on this thread have said should begin to make sense.

I think that your other sources of disagreement with the rest of us may be due to poorly defined frames of reference.  In particular, the wrong choice of reference frame can obscure the simple relationships between force, distance and energy or work done.  I tried to explore this earlier with my thought experiment with a passenger walking down the aisle of an aircraft.

I have aphantasia myself, so I do have some sympathy with you.  I can't form any kind of internal visual images, but I can form what I can best describe as invisible wire-frame images, that I can freely manipulate and rotate.  I can't see them in any visual sense, but I can sense them.

--- End quote ---

Thanks for the comment. It is possible that others same as you have the wrong model of gases.  What you see in that Wikipedia animation is true for a gas that is at a temperature higher than zero kelvin so applies to air in the atmosphere also.
But all that shown in the animation is random motion so not useful in any way. If you have a sail in there no wind particle of air will collide with the sail from all directions but there will be no net force as all collisions will average to zero.
No when there is wind the particles move in the same chaotic way but on top of that there is a net movement in a particular direction and that will be called wind.

The thing is that you can not just randomly change frames of reference without considering the consequences of doing so. No matter from how many frame of reference you look at the same problem the results need to be the same else you did something wrong (not considered what the change in reference frame changed in how you need to interpret the results).
When I thing about all forces (prefer to think in therms of power for this particular problem as is more useful and less likely to make mistakes) I think in an unmodified reference frame and by that I mean that I do not change the frame of reference for vehicle with the road.
Most people for some reason prefer to have the vehicle not moving when thinking about it and instead the road moves underneath the vehicle thus the reason people started to use a treadmill and that was a good choice as that is isolated from the ground and the air.
When I think in my head I imagine the vehicle still moving and the road is what is stationary so I do not modify the frame of reference.  When for example people stop the vehicle and make the road the one that moves they also need to consider that they also flipped the kinetic energy so now the vehicle kinetic energy is the road kinetic energy and vice versa.
Since treadmill is powered by a motor connected to the grid it has no finite kinetic energy like the vehicle did so if you where to break a bit the treadmill the kinetic energy will not be reduced as it will be the case if you break the vehicle. The treadmill has an external energy source and a speed controller so it will try to maintain the speed.

In any case the propeller cart tested on treadmill works perfectly fine as an analogy and experiment is correct. The only problem with that experiment is that treadmill is to short so there is no time to observe how the cart/vehicle gets to top speed and then starts to slow down. So experiment is just not long enough to show what happens.
Since people can not accept that there is energy storage even if it is a well known fact that air is compressible I changed the air for a solid and so the propeller for a wheel thus my diagram that you likely seen.

When I presented that diagram to my surprise people claimed that the wheel only vehicle in my diagram can move from left to right powered only by the treadmill.
So based on this new info I do not think people misunderstand this problem because of not understanding air or propeller (tho that may still be a factor) but they just do not understand the conservation of energy.
I think I expressed fairly clearly that power available to motor wheel comes only from generator wheel and so in real world Motor wheel will have lower power to move vehicle from left to right than the generator wheel opposing that movement trough generating that power for the motor.

If you will be able to understand this problem before other people that likely do not have aphantasia (not very common) then that will mean that phantasia may be more detrimental than helpful for solving this sort of problems.
In any case even those that can form mental images have different levels. I think I'm somewhere average and on the other end there are people that have such vivid mental images that can not even distinguish from real images and that is way more of a problem than not having any mental image.       

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