Down wind faster than the wind

[humber]

Speak for yourself. If someone actually takes this bet up with me, we'll be putting the money in an escrow account and neither side will be able to back out once in place.


There's a guy at our local Arby's that always sits there alone and seems to be having half of an incoherrent discussion about physics. I wonder if humber is in an Arby's somewhere across the country having the other half of that conversation.

He was probably talking about quantum mechanical decoherence. DOH!

 

[sol invictus]

You can put a flag on top of the mountain by answering the question about the failure of the treadmill in a van.

Like probably everyone else reading this thread, I have no idea what you're trying to ask.

Maybe you're asking how one would falsify the equivalence of inertial frames, but you're so incoherent that's just a guess.

 

[humber]

Like probably everyone else reading this thread, I have no idea what you're trying to ask.

Maybe you're asking how one would falsify the equivalence of inertial frames, but you're so incoherent that's just a guess.

I have posted this question three times.

The treadmill and cart are set running at a belt speed of 10mph.
This is put in a van, and driven downwind to wind speed of 10mph.
The behavior of the cart is then said to agree with those conditions, so validating the model, and by inference, the equivalence of the 'treadmill wind' to still air.

What then would indicate a failure, and how would you explain it?

 

[sol invictus]

I have posted this question three times.

The treadmill and cart are set running at a belt speed of 10mph.
This is put in a van, and driven downwind to wind speed of 10mph.
The behavior of the cart is then said to agree with those conditions, so validating the model, and by inference, the equivalence of the 'treadmill wind' to still air.

What then would indicate a failure, and how would you explain it?

Still no idea what you're asking. Sorry.

 

[humber]

Still no idea what you're asking. Sorry.

I actually got that example from Myriad, though other equivalent experiments have been put forward.
The idea being that the cart's performance is indistinguishable from the external situation. There is no wind outside, due to windspeed travel, and the cart agrees by indicating that it is at windspeed.

 

[spork]

Still no idea what you're asking. Sorry.

Try and keep in mind that only half the words get typed out. The rest are still in his head. There's no telling whether it'd be more or less terrifying to get the whole thing.

 

[Brian-M]

That is the problem. You need more power from exactly the same source. Brian-M's device indicates you DO need more force.
There is an error that leads to the conclusion that F = Fc/2. (#925)

The ratio of the gray gears demands that F = Fc, meaning twice the force of a standard cart, for twice the velocity.

By Ft = Fc/2 I meant that the force with which the the cart advances would be half the amount being applied to it by the conveyor belt, which is the same thing as saying Fc = 2Ft, or the force being applied by the conveyor belt is twice the force whith which the cart is advancing, so I think we're in agreement here.

So, the cart advances to twice the speed of the board pushing it, with twice the... (drag? backward force?)... of a cart that advances to the same speed as the board.

Now what if, instead of being pushed by a board, the top wheel was being pushed by the wind? You wouldn't have to worry about running out of length on the board. Of course, you'd have to redisign it a bit, replacing the top wheel with a propeller to get enough "traction", and it would be highly inefficient, advancing with even less force than it would with the board, but it would still work on the same principle.

So, the cart advances to twice the speed of the wind pushing it, with twice the... (drag? backward force?)... of a cart that advances to the same speed as the wind.

It all makes perfect sense... eventually.

 

[spork]

It all makes perfect sense... eventually.

Not if you don't want it to (humber will explain).

 

[Michael C]

Transformation is exactly what Brian M's cart does: it transforms a force of Fc over a distance x into a force of Fc/2 over a distance of 2x. Nothing unusual there.

A transformer cannot give power gain! Only change the ratio of V to F.

Transforming a force of Fc over a distance x into a force of Fc/2 over a distance of 2x does not indicate power gain. The work done (Force times Distance) remains constant.

You are confusing the apparent acceleration of the vehicle, with power gain.

If the conveyor belt is moving at a constant speed, the cart also moves at a constant speed (twice as fast). The vehicle will only accelerate if the onveyor belt accelerates.

 

[H'ethetheth]

Well, thank you, but I was thinking of evidence of performance. The only evidence I have seen, is a cart being blown in the wind at some indeterminate velocity. The direction of the propeller is also vague and aliasing makes it impossible to be sure.

The performance is in there, look.
I have explained that for certain sizes of prop and wheels the cart will accelerate and will not stop accelerating until it reaches wind speed. From the treadmill experiment we can observe that the thrust is non-zero at wind speed. This means that I cannot quantify the performance, but I can qualify that it is going to go faster than the wind.
Furthermore, the direction of the propeller is not vague, it can be seen in many of the videos, and more importantly, if it were the other way around, the cart would never be able to go faster than the wind.

My turn to say fair enough.

The treadmill and cart are set running at a belt speed of 10mph.
This is put ina van, and driven downwind to wind speed of 10mph.
The behavior of the cart is then said to agree with those conditions, validating the model, and by inference, the equivalence of the 'treadmill wind' to still air.

What then would indicate a failure, and how would you explain it?

I don't have a lot of time at the moment, but I agree that these situations are equivalent. I'm not sure what you mean by "failure" in this respect. Do you mean 'what would falsify this equivalence'?
If so, then any significant difference in behaviour compared to a stationary tredmill would falsify it (e.g. cart going backward, or twice as fast or only just faster than the ground outside).
To explain such a difference, I have to say, I would probably have to think about what the hell my education has been good for. After that some people smarter than me would have to overthrow physics.

ETA:A question for my own understanding of your viewpoint: How fast is the earth travelling?

 

[Michael C]

I have posted this question three times.

The treadmill and cart are set running at a belt speed of 10mph.
This is put in a van, and driven downwind to wind speed of 10mph.
The behavior of the cart is then said to agree with those conditions, so validating the model, and by inference, the equivalence of the 'treadmill wind' to still air.

What then would indicate a failure, and how would you explain it?

I'll have a shot at trying to understand what you mean here. I'll say what I think you mean, then you can correct me if you meant something else:

(To avoid confusion, I shall not talk about "downwind" and "upwind", but imagine that we are looking at the experiment directly from the side, so we can use the directions "right" and "left".)

- The wind is blowing at a speed of 10 mph, towards the right.
- The van is moving at a speed of 10 mph, towards the right.
- The treadmill is placed inside the van so that its surface is moving at 10 mph towards the left, relative to the van.
- The cart is on the treadmill, stationary with respect to the van.

Here's a diagram:

Let's compare the cart in the van with a cart on the road running at 10 mph to the right:

1: The cart on the road.

- The air is moving to the right at 10 mph relative to the ground.
- The cart is stationary relative to the air surrounding it.
- The cart is moving to the right at 10 mph relative to the surface of the ground. Since its wheels are touching the ground, they are being turned by this movement.

2: The cart in the van.

- The air in the van is moving at the same speed as the van, so it is moving at the same speed as the air outside: 10 mph relative to the ground.
- The cart is stationary relative to the air surrounding it.
- The surface of the treadmill is moving to the left at 10 mph relative to the van. Since the van is moving to the right at 10 mph relative to the ground, the surface of the treadmill is stationary relative to the ground.
- The cart is moving to the right at the same speed as the van relative to the ground: 10 mph. Since the surface of the treadmill is stationary with respect to the ground, the cart is moving to the right at 10 mph relative to the surface of the treadmill. Since the wheels of the cart are touching the surface of the treadmill, they are being turned by this movement.

The relations between cart, air surrounding it and surface on which its wheels are rolling are the same in each case.

 

[spork]

We've had a couple of people ask us for the parts to build one of these carts. I'd like to be able to send out a parts kit that makes it easy for people to try it for themselves without them having to hunt down all the right parts from various sources. If I have 10 or so people that are interested, I think it would make sense (to minimize shipping costs and part out those things that come in multiples, etc.).

If I do this I do not intend to make any profit at all on it. On the contrary. I'll just put together the parts kit and pass it along for cost. I expect the cost to be in the neighborhood of $30 or so, and it will still require a little bit of basic hobby skills to put it together.

Please let me know if you'd be interested in one.

 

[sol invictus]

I actually got that example from Myriad, though other equivalent experiments have been put forward.
The idea being that the cart's performance is indistinguishable from the external situation. There is no wind outside, due to windspeed travel, and the cart agrees by indicating that it is at windspeed.

I still have no idea what the question is. But regardless, the quote above shows you totally misunderstood Myriad's point. The laws of physics tell us that the speed of the van is totally irrelevant so long as its windows are closed and it's traveling at a steady rate on a smooth road (no bumps). It makes no difference what the wind speed outside is, let alone whether the van moves at that speed.

If the cart on the treadmill in the van behaved differently (e.g. it moved up the treadmill belt in one case and down it in the other) when the van was moving at different speeds, Newton's laws, Einstein's relativity, and most of the other laws of physics would be falsified (again, assuming the ride is smooth and the van's speed is constant during each test).

 

[humber]

By Ft = Fc/2 I meant that the force with which the the cart advances would be half the amount being applied to it by the conveyor belt, which is the same thing as saying Fc = 2Ft, or the force being applied by the conveyor belt is twice the force whith which the cart is advancing, so I think we're in agreement here.

So, the cart advances to twice the speed of the board pushing it, with twice the... (drag? backward force?)... of a cart that advances to the same speed as the board.

Now what if, instead of being pushed by a board, the top wheel was being pushed by the wind? You wouldn't have to worry about running out of length on the board. Of course, you'd have to redisign it a bit, replacing the top wheel with a propeller to get enough "traction", and it would be highly inefficient, advancing with even less force than it would with the board, but it would still work on the same principle.

So, the cart advances to twice the speed of the wind pushing it, with twice the... (drag? backward force?)... of a cart that advances to the same speed as the wind.

It all makes perfect sense... eventually.

Brian-M,
A real object's velocity is governed by the power that is available from the source. The gears cannot offer a power gain. Perhaps there will be some change the acceleration, but not the terminal velocity, which will be the same for the same object without gears. The same for an equivalent propeller driven object. Considering that is a major difference of opinion within this thread, we can leave it at that for the real case.

Some confusion. There is your geared cart and the "skateboard" device. They have different limitations because in the latter case, the velocity increases in the direction of the hand, whereas yours is opposite.

On your device, if you pull at 1m/s backwards, then the cart moves 2m/s forward. Correct?

The graph with the sine waves shows that the average difference will be zero, meaning that your velocity gain, is only incrementally 2. That means that to get the gain, the cart must constantly accelerate.
You know what that means for the input power and the cart's final velocity.

To keep the track at a constant velocity (-V) and the cart at (2V), is not directly possible. To solve this, the average force must controlled. The cart is allowed to accelerates a bit above its average velocity, and then allowed to slow below it by the same amount. (which can be incrementally small).
When calculated using the integral rather than the instantaneous values, you will see that there is no gain over a standard device. If you trade, v for f to gain an improvement, that will also be seen in a standard cart.

Try it. To get the gain, the cart must constantly accelerate.
If the bottom wheel does two revolutions, then the top wheel will turn once. So at that point, you are already at 2V. And from there?

Give the cart some mass, and then apply a constant force or constant velocity.

ETA:
There is nothing wrong with you kinematic collision calculations of an ealrier post . The momentum exchange is not the point. It relates to the way "equivalence" is being misapplied, and the consequences for the cart and treadmill. I am not sure that re-stating it would help

 

[humber]

I'll have a shot at trying to understand what you mean here. I'll say what I think you mean, then you can correct me if you meant something else:

(To avoid confusion, I shall not talk about "downwind" and "upwind", but imagine that we are looking at the experiment directly from the side, so we can use the directions "right" and "left".)

- The wind is blowing at a speed of 10 mph, towards the right.
- The van is moving at a speed of 10 mph, towards the right.
- The treadmill is placed inside the van so that its surface is moving at 10 mph towards the left, relative to the van.
- The cart is on the treadmill, stationary with respect to the van.

Here's a diagram:

[qimg]http://www.internationalskeptics.com/forums/imagehosting/16612492d05622bfd1.jpg[/qimg]

Let's compare the cart in the van with a cart on the road running at 10 mph to the right:

1: The cart on the road.

- The air is moving to the right at 10 mph relative to the ground.
- The cart is stationary relative to the air surrounding it.
- The cart is moving to the right at 10 mph relative to the surface of the ground. Since its wheels are touching the ground, they are being turned by this movement.

2: The cart in the van.

- The air in the van is moving at the same speed as the van, so it is moving at the same speed as the air outside: 10 mph relative to the ground.
- The cart is stationary relative to the air surrounding it.
- The surface of the treadmill is moving to the left at 10 mph relative to the van. Since the van is moving to the right at 10 mph relative to the ground, the surface of the treadmill is stationary relative to the ground.
- The cart is moving to the right at the same speed as the van relative to the ground: 10 mph. Since the surface of the treadmill is stationary with respect to the ground, the cart is moving to the right at 10 mph relative to the surface of the treadmill. Since the wheels of the cart are touching the surface of the treadmill, they are being turned by this movement.

The relations between cart, air surrounding it and surface on which its wheels are rolling are the same in each case.

Yes, that is what I meant. Thanks.
The experiment is not valid unless it is falsifiable. In this case you are given the same answer in all possible cases. Yes, all the velocities add up to agree, but that is for ( and only for) any speed that matches the belt, including zero.

That is rather like saying a clock with no hands is always right.

 

[humber]

I still have no idea what the question is. But regardless, the quote above shows you totally misunderstood Myriad's point. The laws of physics tell us that the speed of the van is totally irrelevant so long as its windows are closed and it's traveling at a steady rate on a smooth road (no bumps). It makes no difference what the wind speed outside is, let alone whether the van moves at that speed.

If the cart on the treadmill in the van behaved differently (e.g. it moved up the treadmill belt in one case and down it in the other) when the van was moving at different speeds, Newton's laws, Einstein's relativity, and most of the other laws of physics would be falsified (again, assuming the ride is smooth and the van's speed is constant during each test).

They are irrelevant, of course. That is the point. The cart is oblivious to its surroundings or the velocity of the van. The outcome of the experiment is unfalsifiable.

 

[Michael C]

This is your reasoning, I think.
Follow the force through from the circumference of the top wheel. The ratio between the wheel and gear is 2, so the force is doubled. The bottom wheel has a ratio of 4:1 dividing it by 4, so in total, it is halved. Fc = F/2, but Vc = 2V, so it goes twice as fast for the same input. Yes?

Yes, ignoring losses from friction. The total work done is conserved. Of course there is always a loss from friction, which means that the tractional force it can produce will be less than half the force provided by the conveyor belt. That's not a problem: we're not asking it to pull a heavy load, and in particular we're not asking it to produce the same force as the belt. The speed ratio stays at 2 to 1: if the wheels don't slip on the belt, the velocity of the cart is twice that of the conveyor belt above it.

The relative velocity of the vehicles is first derived. The force "gain" is derived. The 'mistake' is to equate the two so directly.

Apply 10N, to a 1kg cart for 1s. Note the final velocity of the vehicle. However, in reality, there are retarding forces. Without this consideration, you have simply provided another example of a vehicle that can be accelerated to any velocity, if you apply a force for long enough!.

Sorry, I failed to point that out earlier F= Fc, when V = Vc. No difference in force, or velocity because of the gears. I did include a drawing in my reply to Brain-M, where parachutes provide the force.

There are the retarding forces of friction and drag. The final velocity is reached when there is no more force available to accelerate the vehicle any further. The incremental acceleration is zero.
What is being done here is to modify the way that the vehicle gets to that terminal velocity. There is only enough power to drive it to the same velocity as an equivalent vehicle without gears.

Congratulations: you have just proven that no machine can ever produce an output that is faster than the input. Guess I'd better throw away my bicycle, and the egg-whisk I just bought, because according to you they can't work.

A general comment, Michael_C. It does not apply to all followers.
I don't need to test it, nor should you, unless you can find very good reason to doubt those very centuries tell you that it will not work.

If you do believe in the rules of physics, it is not within those rules to manipulate the ratios of V to F, while ignoring the work that must be done.

Yes, you do need to build the cart: you are misunderstanding the rules of physics and it looks as if only a practical experience could make you change your mind.

 

[humber]

The performance is in there, look.
I have explained that for certain sizes of prop and wheels the cart will accelerate and will not stop accelerating until it reaches wind speed. From the treadmill experiment we can observe that the thrust is non-zero at wind speed. This means that I cannot quantify the performance, but I can qualify that it is going to go faster than the wind.
Furthermore, the direction of the propeller is not vague, it can be seen in many of the videos, and more importantly, if it were the other way around, the cart would never be able to go faster than the wind.

Well, I did look. Which is why I have studied the propellor rotation.
There are no videos with recorded velocities. There are no comparisons with a non-geared cart or sail cart, under the same conditions. I have to accept windspeed travel as an absolute given fact. That is not evidence.
Post hoc explanations are not evidence.

The treadmill fails on several counts.
1 It is not falsifiable, as explained below.
2. Even at windspeed, an acceleration of zero means that there is no incremental force required; no more than the force required to keep it at the same velocity. The cart does not show that constant force, or consume the power to do so. It can be pushed back with ease.
However, all results are in accord with what is required to keep a toy moving on a treadmill under the same low friction, low load conditions.

I don't have a lot of time at the moment, but I agree that these situations are equivalent. I'm not sure what you mean by "failure" in this respect. Do you mean 'what would falsify this equivalence'?
If so, then any significant difference in behaviour compared to a stationary tredmill would falsify it (e.g. cart going backward, or twice as fast or only just faster than the ground outside).
To explain such a difference, I have to say, I would probably have to think about what the hell my education has been good for. After that some people smarter than me would have to overthrow physics.

ETA:A question for my own understanding of your viewpoint: How fast is the earth travelling?

Those results could have a simple explanation. Rapid acceleration of the van would perhaps throw the device about, but that is not the claim, and would be a problem for the hypothesis if included.

You can choose the velocity of the earth, if you wish. If I can change the van's velocity relative to the wind or ground or beltspeed, and still get the same result, then that can't possibly matter. The same outcome of "windspeed travel" occurs in all conditions, all directions. It is an unfalsifiable indicator of windspeed travel.
However, all is in accord with a van with a toy on a treadmill being driven around town.

 

[humber]

Yes, ignoring losses from friction. The total work done is conserved. Of course there is always a loss from friction, which means that the tractional force it can produce will be less than half the force provided by the conveyor belt. That's not a problem: we're not asking it to pull a heavy load, and in particular we're not asking it to produce the same force as the belt. The speed ratio stays at 2 to 1: if the wheels don't slip on the belt, the velocity of the cart is twice that of the conveyor belt above it.

But you must have the same power input, plus the frictional losses.

The scheme only works as you describe if it can constantly accelerate.

Do the maths, draw some graphs. Include real times and distances, then tell me it is not true.

May be the sines don't mean much to you, but thet show that the velocity gain is incremental. I though it would help.

Congratulations: you have just proven that no machine can ever produce an output that is faster than the input. Guess I'd better throw away my bicycle, and the egg-whisk I just bought, because according to you they can't work.

No, see the above comment, and my reply to Brain-M. Your velocity increase is a re-iteration of f=ma.

Yes, you do need to build the cart: you are misunderstanding the rules of physics and it looks as if only a practical experience could make you change your mind.

A. Built similar wheel-driven propeller windcart aged 10
B. Built geared vehicle, pulled by string wound around a shaft, around same time. Also tried flywheels.
C. Connected DC motors to DC generators to see what would happen.
D. Various other "ideas". I learned that you can't control a 1HP motor with a 10K potentiometer.

I now know better not to try without first thinking.

 

[humber]

Double post.