Down wind faster than the wind

sol invictus · Nov 30, 2008

humber said:
A sailed vehicle cannot travel faster than a steady wind,

Denial of reality really isn't going to get you very far in life.

but a vehicle in variable wind may travel faster than the wind if it can gather enough energy from those bursts, and then deploy it as needed.

Sure, whatever you say.

If the vehicle's velocity is measured by a timed trial, then this will lead to an error, because the 'average' windspeed may vary over that period.

Or it may not. Along with your total ignorance of physics, you obviously have no experience with sailing. I'm sure the participants and spectators at iceboat races (where the boats' speeds can exceed 60 mph) will be shocked to hear about the 60 mph gusts they were evidently being exposed to, when all they felt was a gentle 10 mph wind.

I accept them in preference to believing that a cart on a treadmill is really going at windspeed, and best of all, driving it around in a car proves it.

To satisfy our curiosity about the workings of your brain, why not tell us exactly what force acts on the cart on the treadmill (and accelerates it against the belt, as you've accepted) that doesn't acting on the cart moving down a smooth path at windspeed?

Dan O. · Nov 30, 2008

We can also forget about the mechanical details and just analyze the physics involved.

The cart is traveling with the wind at 1 meter/second. Extracting 1 watt of power from the forward motion creates a breaking force on the cart of 1 newton (1 watt = 1 Newton•meter/second). The 1 Newton breaking force can be countered by accelerating a 1 kilogram mass of air surrounding the cart backwards at 1 meter/second each second (1 Newton = 1 kilogram meter/second/second). This requires only 1/2 watt of power (E=1/2 MV²; 1/2 • 1 kilogram•(1 meter/second)² = 1/2 Joule; 1/2 Joule/second = 1/2 watt). We then have leftover an extra 1/2 watt of free power.

Michael C · Nov 30, 2008

Michael C said:
This works both with and without "real wind". Do you honestly believe that a treadmill without "real wind" is useless, and one with "real wind" is useful?

humber said:
In the no wind case, it is a dyno.

Ever tried running on a dyno?

So you're still saying that if there's a "real wind", the treadmill is useful, but it's not useful if there isn't a "real wind"?

How much "real wind" does there have to be? Is 1 kmh enough?

Michael C · Nov 30, 2008

Michael C said:
So according to you, if an object is stationary with respect to the air, the air can be having no effect on it? Or if it is stationary with respect to the ground, the ground can be having no effect on it?

John Freestone said:
They're having effects on each other of all sorts, but in terms of the relevant mechanics, that is absolutely bog standard. Any engineer should be able to confirm this. You can't gain momentum from a null relative motion, no matter what's happening relative to other things.

No, you cannot gain energy from nul relative motion. The energy for the DDWFTTW cart is coming from the relative motion between the wind and the ground: no problem there.

ynot · Nov 30, 2008

spork said:
In fact it can. Land yachts attain a downwind velocity component greater than the wind as an everyday affair. This is not even in contention. The trick is to come up with a clever way to do that same thing while going DIRECTLY downwind. For $40 you can do exactly that.

As I understand it land yatchs can only go faster than the wind directly downwind using speed they have developed and stored from first going diagonal to the wind at a speed faster than the wind (but not with it). Once this stored speed is used up they would slow down to a speed less than the wind. There is no argument that it‘s possible to travel faster than the speed of the wind at an angle to it, but not directly with it.

spork said:
Then please allow us to explain using simplified examples.

Please do.

spork said:
But you have to ask, why would we build these carts, post these videos, debate this on internet forums, and describe how to build your own, only so we can be shown to be fakes. I can't imagine what upside there would be to faking this. We've invested a ridiculous amount of time into this silly thing only as some sort of perverse hobby (we love being insulted). Even the parts kit I've offered, I'm offering at my cost of parts - and I expect to put at least a couple hundred bucks worth of my own time into each one I send out.

I also have to ask why some people stay up late at night and spend their valuable time creating complex crop circles, and all the other weird and wonderful things people do.

spork said:
I can hardly believe that you're not happy with the videos. But you seem to be willing to believe given the right evidence. So I'll tell you what... give me an EXACT script for the test you want to see and I'll do it. Don't leave anything out. Do you need to see a level? Do you need us to move the cart through the handle a few times to prove there's no string? Should I pan the camera to prove there's no fan? I know you've done it before, but indulge me. Tell me exactly what you want to see and tomorrow you will see just that.

This video is an example of bad testing - http://www.youtube.com/watch?v=dgHBDESd38M&fmt=18

Why are you testing so close to the botom roller when this is the very worse position to test in? As these guys said in this video - http://www.youtube.com/watch?v=9S2HHwfcz9Y “there is a pit just in front of the roller” The best place to test is obviously in the middle of the tread.

Of all the ways you can choose to keep the cart centred of the tread why do you choose to deform the flatness of the belt by placing boards under both sides of it? Why wouldn‘t this effect the whole width of the belt and have some effect on the action of the cart? Hardly good science.
In the video the cart “rocks” back and forth between the “pit” of the roller and the “bump” created by the boards under the belt (the cart is effectively surfing). Before the filming started I believe the cart was held against the belt so it stored kinetic energy beyond what it needed to overcome the rolling resistance of the wheels. Over the course of the video this stored energy is used up and the cart eventually falls off the back of the tread. As I see it this video does more to prove the cart is using stored energy than I doesn’t. The cart never even got close to the top end of the tread and it was never a toss of a coin that it ever would. Why does someone say - “It’s not scientific, its all kinetic energy”? What is meant by this? As I see it not only is it “all kinetic energy“, it’s all stored kinetic energy.

I thought I had given you an EXACT script for the test. It really is quite simple. Here it is again - Tether your cart (from the front of your cart) to a fixed point off the top end of the centre of the tread so that the string extends down the centre of the tread and the cart is held not too close to the bottom roller (just lower than the center of the tread). The string should keep the cart self-centred and it shouldn‘t need to be touched at all. Start the tread at it’s slowest speed and gradually increase the speed until the moment the propeller develops enough thrust to move the cart against the motion of the tread. The string will become slack. DON’T speed the tread up anymore and see if (given enough time) the cart eventually moves backwards with the tread and the string becomes taught again.

As this test is designed to see if the cart is using stored kinetic energy to move against the motion of the tread, giving the tread a slight uphill angle will speed up the loss of that stored energy. The loss of the stored energy while active on the tread is not accurately represented by the loss observed when the cart is removed from the moving tread. It’s much slower and more gradual so a reasonable amount of time must be given in this experiment for this to happen.

I think that‘s it. Do you require any more?

humber · Nov 30, 2008

Brain_M,
Perhaps we should start again. Here is your cart from #925.

And abridged calculations.

Your conclusion regarding force is not correct. All the elements are in series, so there is but one line of force that flows from the applied force to the ground. Apart from that, you can see that this must be true, by stacking the gears so that you include all of their relationships.

When done:
Ft = Fc
St = Sc

But, if the direction of the applied force is changed, then the velocity differential is 3, but as you note, when moving it is reduced by 1, so St = 2Sc. Yes, but then for the same acceleration, F must double.

This is all to be expected from preservation of the power input. This cart will behave no differently from a standard mass, except that there will be the inertial mass of the rotating elements to consider. The final velocity of a geared or standard cart will be determined by the input and retarding forces.

spork · Nov 30, 2008

ynot said:
As I understand it land yatchs can only go faster than the wind directly downwind using speed they have developed and stored from first going diagonal to the wind at a speed faster than the wind (but not with it). Once this stored speed is used up they would slow down to a speed less than the wind. There is no argument that it‘s possible to travel faster than the speed of the wind at an angle to it, but not directly with it.

You don't understand correctly. What I said is that an ice-boat can maintain a 45 degree downwind tack such that its downwind velocity component is 3X to 4X wind speed. Do you understand and agree with that?

I also have to ask why some people stay up late at night and spend their valuable time creating complex crop circles, and all the other weird and wonderful things people do.

Fair enough. Are those people on the internet telling you exactly how to do it, and offering parts kits at cost at considerable time expenditure of their own.

This video is an example of bad testing - ...Why are you testing so close to the botom roller when this is the very worse position to test in? As these guys said in this video ... “there is a pit just in front of the roller” The best place to test is obviously in the middle of the tread.

Boy, people sure are awfully damn demanding and critical of others that offer their time for free and with no hope of any gain. Your skepticism does not equate to bad testing on our part. And I suggest you think awfully hard before you decide to explain good science to me.

As to the "pit", our cart weighs 5.7 oz. There is probably 2 oz of weight on the rear wheel. I assure you it doesn't settle into a pit on the belt of my treadmill. For god's sake, you want to see the thing maintain unassisted. We went to a good deal of trouble to make it do exactly that. I assure you that both you and everyone else will have a problem with absolutely any test we do. In fact I'm confident that I could plant your butt in the seat of a full sized cart, strap you in (against your will - since you really don't want to believe), give you a GPS and wind instruments, and set you on your way downwind, faster than the wind - and you still would not believe. So clearly I'm the stupid one for wasting my time.

Of all the ways you can choose to keep the cart centred of the tread why do you choose to deform the flatness of the belt by placing boards under both sides of it?

We turn the edges of the belt up to keep it from going off either side. I can give you my absolute 100% guarantee that no matter what we did, it wouldn't be good enough.

Hardly good science

With all due respect - KISS MY A$$ You want to pull out credentials and compare? What have you learned about science by shaking a sign beside the road?

In the video the cart “rocks” back and forth between the “pit” of the roller and the “bump” created by the boards under the belt

No it does not. The prop is in cleaner air behind the belt (less gradient). That's why it's hovering there.

Before the filming started I believe the cart was held against the belt so it stored kinetic energy beyond what it needed to overcome the rolling resistance of the wheels.

Yes, and then our one ounce prop doled out that kinetic energy over the next 1 minute, 48 seconds, even though we show that it will coast to a stop in under 7 seconds on its own. Good thinking.

The cart never even got close to the top end of the tread and it was never a toss of a coin that it ever would.

As I said many times, we went to a good deal of effort to get it to "hover". It can't very well advance on the treadmill and stay on it indefinitely at the same time. Take your pick genius.

Why does someone say - “It’s not scientific, its all kinetic energy”? What is meant by this?

It's a sarcastic comment refering to a not so sharp critic that made exactly the same comment you have about stored energy.

I thought I had given you an EXACT script for the test.

I'm sure you have. I didn't plan to go back and find it. I planned to do your silly test today, and in fact went down to feel for the "pit" in my treadmill in the middle of writing this response. But screw your test. I really don't care if you believe. This problem sort of takes care of itself in that the tests and explanations I've given have been more than sufficient for anyone that I have the slightest intellectual respect for.

Do you require any more?

Gosh no. That'll be plenty.

humber · Nov 30, 2008

Michael C said:
Ever tried running on a dyno?

That is what a domestic treadmill is, save that you generate all the energy required to move your muscle mass, and then dissipate it to the air mostly as heat.

So you're still saying that if there's a "real wind", the treadmill is useful, but it's not useful if there isn't a "real wind"?

How much "real wind" does there have to be? Is 1 kmh enough?

Real wind is required to test the vehicle for aerodynamic efficiency, and against that real load. If there is no wind, then there is no load, so the engines' power is absorbed by the dyno's load.
The vehicle need only be restrained to take up any difference that may occur between the generated forces, and that absorbed by the dyno load.
In principle, the vehicle can remain stationary, but restraint (often by the front wheels) is not necessary if a control loop can be maintained between the car and the dyno.
They do not build those enormous fans for nothing.

Michael C · Nov 30, 2008

Michael C said:
Ever tried running on a dyno?

humber said:
That is what a domestic treadmill is, save that you generate all the energy required to move your muscle mass, and then dissipate it to the air mostly as heat.

You're sure of that? A domestic treadmill is a dyno? Would you care to place a bet on that?

humber · Nov 30, 2008

sol invictus said:
You're correct that standard sailed vehicles cannot sail directly downwind faster than the wind.

Humber
A sailed vehicle cannot travel faster than a steady wind,

Your conclusion, and Oprah's advice...

sol invictus said:
Denial of reality really isn't going to get you very far in life.

The workings of your mind. Cognitive dissonance.

Sure, whatever you say.

See the role information plays in entropy. You don't seem to be aware of the concept.

Or it may not. Along with your total ignorance of physics, you obviously have no experience with sailing. I'm sure the participants and spectators at iceboat races (where the boats' speeds can exceed 60 mph) will be shocked to hear about the 60 mph gusts they were evidently being exposed to, when all they felt was a gentle 10 mph wind.

I have already said that I am no sailor, but even still, more than you are a physicist.
It is only necessary to have some gusts over the average. The more the merrier of course, but in principle it is only necessary to accumulate enough momentum to achieve the required velocity against the retarding frictional and drag forces.

Not having a scientific background the audience may not realise, that all measurement necessary to the energy calculations, must be made from the craft itself, or errors may occur. Oh...I see.
I wonder if such events are are held, or those high speeds obtained, only when the wind is suitable?

To satisfy our curiosity about the workings of your brain, why not tell us exactly what force acts on the cart on the treadmill (and accelerates it against the belt, as you've accepted) that doesn't acting on the cart moving down a smooth path at windspeed?

Rather a lot there. I doubt that you would understand the answer, so I will stick to the direct question.

The belt drives the wheels. The propeller is driven from the same source via the gearbox. The only load for the belt is therefore that presented by the propeller's drag as it spins aimlessly in the air.

The torque so generated is in opposition to that from the wheels. The net force, that which drives the cart, is the difference that remains from that balance. That you will appreciate is quite small.

It follows that that absolute force that can be sustained is limited by the friction between the wheels and the belt, which as can be seen from the video, is very low.
You may draw your own conclusion for the consequences that would have for a real vehicle traveliing at windspeed.
There are many consequences, but as a model, the inferred frictional requirement is "treadmill dependent", as is the resultant driving force. Colossal failure.

sol invictus · Nov 30, 2008

humber said:
The workings of your mind. Cognitive dissonance.

So not only are you not capable of understanding high school physics - you can't read either. I'll give you a hint:

sol invictus said:
You're correct that standard sailed vehicles cannot sail directly downwind faster than the wind.

Does that make it easier?

See the role information plays in entropy. You don't seem to be aware of the concept.

I'm an expert on that topic, actually. It has absolutely nothing to do with this.

I have already said that I am no sailor, but even still, more than you are a physicist.

I have refrained from mentioning my credentials for good reason, and I will continue to do so. Suffice it to say you're as utterly wrong in this as in every other thing you've said.

Not having a scientific background the audience may not realise, that all measurement necessary to the energy calculations, must be made from the craft itself, or errors may occur.

Nonsense.

Oh...I see.
I wonder if such events are are held, or those high speeds obtained, only when the wind is suitable?

Yes - when it's steady and not too strong. I've attended one of these races in person, by the way, and I've often been around iceboats (although I've never sailed one). Not to mention windsurfers and sailboats.

Rather a lot there. I doubt that you would understand the answer, so I will stick to the direct question.

You didn't answer the question. Again - what force acts on the cart on the treadmill that does not act on a cart traveling at the speed of the wind? It's a simple question, with a very simple answer.

humber · Nov 30, 2008

Michael C said:
You're sure of that? A domestic treadmill is a dyno? Would you care to place a bet on that?

It makes no difference to the situation with the car. You have ignored that in preference to the straw man of the human treadmill.

A domestic treadmill is a dyno. The idea is not to use the motor's power, or there would be no point, but it is necessary to have some movement so that the runner can remain stable. Before you continue, you should study what actually happens when a human walks or runs. We are "quasi stable", almost falling over, before we regain our balance.
The alternative of running against a loaded belt and holding on to a rail, makes running difficult so sales would plummet.

humber · Nov 30, 2008

sol invictus said:
So not only are you not capable of understanding high school physics - you can't read either. I'll give you a hint:

Pettifoggery, to cover up your usual approach of reading what suits you.
The meaning is the same.

Yes - when it's steady and not too strong. I've attended one of these races in person, by the way, and I've often been around iceboats (although I've never sailed one). Not to mention windsurfers and sailboats.

Good, I've been to a football match.
You are an "expert" in this field, and you are unaware that if you do not make all measurements locally to the craft, errors will arise?
( See Formula one in-car telemetry)
And that the operator cannot add information, by the observation of future events for example, and gain advantage over a strictly steady state vehicle ?
You can post your credentials, but don't put denial of that in your CV or resume.
ETA:
Or even statistically?

You didn't answer the question. Again - what force acts on the cart on the treadmill that does not act on a cart traveling at the speed of the wind? It's a simple question, with a very simple answer.

Yes I did. Force that is greater than the arbitrary level obtained due to stray friction in the treadmill.
To obtain windspeed, there will be a static force to maintain it in place; that is not present. Even allowing for that obviously false premise, the amount of force shown by the cart as it "accelerates" is a defined by the characteristics of the treadmill. A road will differ in that respect alone.
Then again, I am forgetting that you are the "expert" that told me that the ground of the treadmill is "the wheels, of course"

ynot · Nov 30, 2008

spork said:
You don't understand correctly. What I said is that an ice-boat can maintain a 45 degree downwind tack such that its downwind velocity component is 3X to 4X wind speed. Do you understand and agree with that?

45 degrees is not travelling directly downwind faster than the wind. Perhaps I should tell the NZ America’s Cup team that they shouldn’t raise a large spinnaker and travel directly downwind on the homeward leg, but they should tack from side to side to go even faster than the wind and we will easily win the cup back?

spork said:
Fair enough. Are those people on the internet telling you exactly how to do it, and offering parts kits at cost at considerable time expenditure of their own.

This certainly adds to your credibilty (or perhaps refects your delusion). I remind you that I'm not saying you are definitely faking it, but as the possibility exists that you are it must be considered.

spork said:
Boy, people sure are awfully damn demanding and critical of others that offer their time for free and with no hope of any gain. Your skepticism does not equate to bad testing on our part. And I suggest you think awfully hard before you decide to explain good science to me.

See Above.

spork said:
As to the "pit", our cart weighs 5.7 oz. There is probably 2 oz of weight on the rear wheel. I assure you it doesn't settle into a pit on the belt of my treadmill. For god's sake, you want to see the thing maintain unassisted. We went to a good deal of trouble to make it do exactly that. I assure you that both you and everyone else will have a problem with absolutely any test we do. In fact I'm confident that I could plant your butt in the seat of a full sized cart, strap you in (against your will - since you really don't want to believe), give you a GPS and wind instruments, and set you on your way downwind, faster than the wind - and you still would not believe. So clearly I'm the stupid one for wasting my time.

So repeat your test 10 - 20 times and see if it travels off the top of the treadmill 50% of the time as you claim it should (isn't this is what good science does). I don’t agree with you so your dispassionate scientific conclusion is I am stupid, dogmatic or both.

spork said:
We turn the edges of the belt up to keep it from going off either side. I can give you my absolute 100% guarantee that no matter what we did, it wouldn't be good enough.

The tether string method I have suggested would be fully acceptable (more than good enough).

spork said:
With all due respect - KISS MY A$$ You want to pull out credentials and compare? What have you learned about science by shaking a sign beside the road?

Interesting to remember that Uri Geller’s party tricks completely fooled a bunch of experts with academic credentials and it took the “hack” (no disrepect intended) credentials of Randi to expose him as a fraud. It’s more amazing that many people strill belive that Geller is genuine (hope you‘re not one of them ;-).

spork said:
No it does not. The prop is in cleaner air behind the belt (less gradient). That's why it's hovering there.

So your cart can’t hover in dirty air above the moving tread? Yet you demonstrate it in other videos that not only can it hover but it can advance against the moving treat over the whole length of the belt and off the top

spork said:
Yes, and then our one ounce prop doled out that kinetic energy over the next 1 minute, 48 seconds, even though we show that it will coast to a stop in under 7 seconds on its own. Good thinking.

“The loss of the stored energy while active on the tread is not accurately represented by the loss observed when the cart is removed from the moving tread.”

spork said:
As I said many times, we went to a good deal of effort to get it to "hover". It can't very well advance on the treadmill and stay on it indefinitely at the same time. Take your pick genius.

Show it "hovering" off the top of the tread 50% of the time

spork said:
It's a sarcastic comment refering to a not so sharp critic that made exactly the same comment you have about stored energy.

Understood.

spork said:
I'm sure you have. I didn't plan to go back and find it. I planned to do your silly test today, and in fact went down to feel for the "pit" in my treadmill in the middle of writing this response. But screw your test. I really don't care if you believe. This problem sort of takes care of itself in that the tests and explanations I've given have been more than sufficient for anyone that I have the slightest intellectual respect for.

Gosh no. That'll be plenty.

Please explain exactly what is “silly” about my suggested test. I don’t want to believe I want to know and I don‘t claim that I conclusively do at this stage (as you obviously claim).

The “pit” was not my description of the effect of the roller on the cart. I can’t explain it adequately but I am sure there is some effect that the cart “feels” close to the roller that it doesn’t away from it.

If personal insult is your best argument then your agrument is very weak. Your response is exactly what I get from paranormal believers. You owe me nothing and you don’t have to provide credible and repeated tests of your claims. I don’t have to accept your claims either. As I have said (if I retain and interest to do so) I will build my own cart (or buy yours if you will still sell it to me) and run my own series of tests and publish the results. You can then critsize my tests as I'm sure you would do.

ETA - Perhaps someone else that buys one of your cart kits might like to test their cart the way I have suggested and let us know the results.

Modified · Nov 30, 2008

humber said:
Yes I did. Force that is greater than the arbitrary level obtained due to stray friction in the treadmill.
To obtain windspeed, there will be a static force to maintain it in place, that is not present. Even allowing for that obviously false premise, the amount of force shown by the cart as it "accelerates" is a defined by the characteristics of the treadmill. A road will be different in that single respect.

We assume that the treadmill is large compared to the vehicle, and that the earth is large compared to the vehicle. Acceleration of the vehicle will not significantly accelerate the treadmill belt or the earth, so both can be treated equivalently as non-accelerating surfaces. If the vehicle is large compared to the treadmill or the earth, the performance will be quite different.

humber · Nov 30, 2008

Modified said:
We assume that the treadmill is large compared to the vehicle, and that the earth is large compared to the vehicle. Acceleration of the vehicle will not significantly accelerate the treadmill belt or the earth, so both can be treated equivalently as non-accelerating surfaces. If the vehicle is large compared to the treadmill or the earth, the performance will be quite different.

The ratios are not important. The forces required, and therefore the friction to the surface be it road or belt, are absolute values. Same cart.
Additionally, the total force (drag + beltforce) can be only increased by increasing the drag, because the propeller and wheels are in series to the belt. Because the drive force is (drag - beltforce) ~ 0, increasing the total force would not increase the drive force.

Modified · Nov 30, 2008

ynot said:
45 degrees is not travelling directly downwind faster than the wind. Perhaps I should tell the NZ America’s Cup team that they shouldn’t raise a large spinnaker and travel directly downwind on the homeward leg, but they should tack from side to side to go even faster than the wind and we will easily win the cup back?

Sailboats have a lot of drag. A downwind tack where the apparent wind will allow you to beat the wind provides relatively little force. In an iceboat it's easy to beat the wind.

spork · Nov 30, 2008

ynot said:
45 degrees is not travelling directly downwind faster than the wind. Perhaps I should tell the NZ America’s Cup team that they shouldn’t raise a large spinnaker and travel directly downwind on the homeward leg, but they should tack from side to side to go even faster than the wind and we will easily win the cup back?

Perhaps if you knew the first thing about sailing you'd realize that high performance boats already do exactly this. I don't think they need you to give them the winning secret.

your dispassionate scientific conclusion is I am stupid, dogmatic or both.

Stupid.

The tether string method I have suggested would be fully acceptable (more than good enough).

I'll offer another straight up bet on that. You do that test and we'll see if it convinces anyone. Oh yeah, I forgot, you're just the jackass with a keyboard. You're not going to build anything, do any tests, or offer anything of value at all. But should hell freeze over and you do build a cart and do that test - PLEASE take me up on this bet. You name the amount.

Interesting to remember that Uri Geller’s party tricks completely fooled a bunch of experts with credentials and it took the “hack” (no disrepect intended) credentials of Randi to expose him as a fraud.

So what you're saying is that even if I did your experiment, you still wouldn't believe. But I already knew that.

So your cart can’t hover in dirty air above the moving tread? Yet you demonstrate it in other videos that not only can it hover but it can advance against the moving treat over the whole length of the belt and off the top

MY GOD YOU'RE THICK!

If personal insult is your best argument then your agrument is very weak.

We've provided analysis, build instructions, video, and even done videos in response to any reasonable request. Analysis is clearly beyond you, so I respond to your insults with insults.

Perhaps someone else that buys one of your cart kits might like to test their cart the way I have suggested and let us know the results.

Yes, perhaps someone else will do that since you clearly won't do anything but criticize. I'm sure they'll be happy to jump through hoops for you in the hopes of recieving some of your ill-founded insults.

humber · Nov 30, 2008

The lack of static force cannot be glossed over. Even I accept the notion that the cart can "float" ahead of this force, the incremental force that would accelerate it is that shown in the treadmill. Very small.
If the cart is pushed back against the belt, a large reaction should be manifest. It is not.

If the treadmill notion is correct, it can be quite simply tested by dragging the cart backwards along the floor, in still air. The same "equivalence" rules apply. The cart and wind are locally at the same velocity, with the road going "backwards".
The rotation or bias of the propeller can be changed as necessary, but at some velocity, there should be a point where the applied (reverse) force fall to zero as the cart get is "in the zone".

ETA:
Spork,
You are too irrational to respond intelligibly, even to those that show support, albeit wavering. Before you press the bet button, you should note that I have cached all of the bet posts with you, in a a logged and undeniably authoritative location.
If you are so keen on gambling, that makes me doubt your integrity, because you cannot produce the verifiable evidence of faster than wind performance, even at this point.
If you do want to gamble, you set it up. Do your own dirty work.

Modified · Nov 30, 2008

humber said:
The ratios are not important.

Of course the ratios are important. Try walking around on the deck of a large ship moving at constant speed. The forces are almost exactly the same as on the ground, and you will not be able to tell the difference. Even though your movements do accelerate the ship, the amount of acceleration is negligible. Now do the same in a motorized canoe. Your movements will accelerate the canoe significantly, and things will get a lot more complicated. Similarly, a relatively large vehicle's accelerations will accelerate a treadmill belt, or the earth. The small cart on the treadmill is just like you on the ship. Have you ever been on a large ship? Assuming smooth seas, did you have to walk differently than on solid ground to avoid falling? Why do you think a belt would be any different?

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Philosopher

Philosopher

Philosopher

Graduate Poster

Philosopher

Philosopher