Split Thread The validity of classical physics (split from: DWFTTW)

[humber]

No, but their designers DO use windtunnels, with the car stationary and a "Wind" produced, to simulate the car movingh through still air.

THEY understand it is a model of the real situation, YOU don't.

No, I would ask you to provide evidence that is the case. Not pictures where you have assumed it to be so. Make the effort. Contact them.

No need, though. Solve the KE problem and all will be well.

 

[humber]

No, but their designers DO use windtunnels, with the car stationary and a "Wind" produced, to simulate the car movingh through still air.

THEY understand it is a model of the real situation, YOU don't.

ZERO KE RELATIVE TO WHAT??

Yes, relative to what? The real cart it is relative to the earth/road. This must be so for the treadmill. That means the belt.

You STILL don't get that KE is RELATIVE!! There is no such thing as a "Zero KE" object EXCEPT to an observer matching velocities with it.

That is for any two objects traveling at that same velocity. Being near or far, makes no difference. There are many objects doing this, I need one that is causally related to the cart. That is the belt.

Conversely, ANY object is zero KE to ANY observer at the same velocity as the object, REGARDLESS of what else the object may have relative velocity too.

No, there is an implied specific paring of cart and road.

The surface of the Earth is in NO WAY a special frame of reference.

Yes, that is why we can both make the same claim.

If two media are moving relative to each other, it is ONLY the velocity difference that matters, NOT which media appears to be moving to a third party observer.

Partially true, but it still does not explain the fact that there is no KE local to the cart that can balance the equation to make the KE zero.
You cannot measure it "as is", can you?

 

[RossFW]

No, I would ask you to provide evidence that is the case. Not pictures where you have assumed it to be so. Make the effort. Contact them.

No need, just LISTEN (can you do that?) to what the man says!!

http://video.google.com/videoplay?docid=-1799513879746122105

 

[RossFW]

That is for any two objects traveling at that same velocity. Being near or far, makes no difference. There are many objects doing this, I need one that is causally related to the cart. That is the belt.

Exactly so! The cart has KE relative to the belt. That is a perfectly valid frame of reference.

From the carts POV, it now has a surface moving under it's wheels, and no relative airflow. That is indistinguishable from it being on the road at wind speed. You have some vague, semi-valid point WRT wind gradients (though, as SPORK pointed out, a large enough treadmill belt has the same effect on still air as a stationary road has on moving air) but in terms of the basic physics, you have completely missed the basic premise of the experiment.

 

[Dan O.]

You are suggesting that you cannot walk because the bottom layers of your shoes do not move relative to the ground?

No, that is not correct. If the cart is in real wind, it is immersed in the wind, not at the leading edge of it. There will be wind ahead and behind the cart.
This cart is like an object immersed in a river, but close to the bed. The water flows slower at the shear layer, but not backwards. That can happen, but it is usually a contraflow created by an obstacle, and the flows may even be equal and opposite.

This situation can occur for the belt. The laminar flow can be sen to be equal and opposite to the velocity of travel, which is the case at "windspeed", though the relationship changes at different velocities w.r.t the belt.
This is not the case in real wind. The flow is never reversed.

The belt laminar flow is a contraflow, it "slips under" the air of the room, which is said to be a tailwind. Therefore, it is wrong.

Humber, are you being deliberately stupid? When is the air above the belt ever moving right to left faster than the belt on the treadmill?

Looking at just the treadmill in a room, still air, no fans, no hobos, no cart. The treadmill is facing right just like in Spork's videos. The belt is moving right to left. Where is the air moving right to left faster than the belt?

If your feet were glued to the belt so that you are moving right to left at the speed of the belt, where is the wind that is moving past you right to left?

 

[mender]

Guys, it should be painfully obvious by now that humber is sincere in his misunderstanding. Unfortunately, he has convinced himself that he is right despite all evidence to the contrary. Until he can conceive the idea that he can be wrong, he will not change his mind. Simple as that.

It is readily apparent that he has a working vocabulary that resembles physics but his particular "understanding" appears to me to be book-learned and self-taught. This results in all kinds of disconnects when discussing physics with him. They seem minor by themselves but stack up pretty quickly to effectively prohibit any effectual communication because of how he misinterprets the definitions. I agree with humber that it is not intentional, as expressed many times by humber that he really believes that he is right.

To change his world view would indeed be as "earth-shaking" as convincing a flat-earther that the world is round. It may not be possible for that to happen. I know I'll get some flack for my next statement but I see humber as intellegent (certainly word-wise) but not capable of getting this.

 

[humber]

No need, just LISTEN (can you do that?) to what the man says!!

http://video.google.com/videoplay?docid=-1799513879746122105

Yes RossFW, I have covered this. There is wind. They are measuring the aerodynamics of the car. They say so. CFD is used to modify the input data to simulate lateral movement for example. Big time saver, that is the advantage.
The car is held in place by the section to the roof (that is how they solve the stability problem). That device is symmetrical and of small section so that it does not significantly influence the car, driving into the wind. And it can support a load from the car if need be. Completely different situation.
They do not test for 300kph tailwinds. Races are quite impossible under those conditions. F1 cars are thoroughbreds, that run optimaly only under certain defined conditions. Even rain give them a big problem.

If you really understand the behaviour of a wheeled vehicle on a belt that is powered by that belt, you will see a problem. In principle, it is not possible to transmit power from the belt to the cart, yet have it remain in place on that belt. It is indeterminate.
It sounds odd, but it is true. You think have seen otherwise, but there is always a stabilizing mechanism.
In the F1 case, it is the section to the roof. It could be feedback, but that is difficult. For the orange, it is either a "dip in the belt" or offset COG. In the cart, it is the way that the wheel and propellor are coupled. That simple mechanism, is what supports what you see, not the model itself!

The model is wrongly derived. Yes, the relative velocities may be the same, but you cannot swap the environmental variables, making the road power the wind/cart for example, and make that work to that model.

 

[humber]

Humber, are you being deliberately stupid? When is the air above the belt ever moving right to left faster than the belt on the treadmill?

Not faster, no. Take the position relative to the ground. The belt moves right to left. If the cart advances up that belt it moves left to right. That reveals the differential velocity of belt and cart. The laminar flow moves with the belt, Forget the profile, there is a flow, and that flow can be "backwards" relative to the forward motion of the cart on the belt.
You know that it is possible to translate these velocities back to the belt, so it is arithmetically sound.

Looking at just the treadmill in a room, still air, no fans, no hobos, no cart. The treadmill is facing right just like in Spork's videos. The belt is moving right to left. Where is the air moving right to left faster than the belt?

Again,not faster.

If your feet were glued to the belt so that you are moving right to left at the speed of the belt, where is the wind that is moving past you right to left?

It's not! That's the point. From that position you describe, increase your velocity so that you move up the belt. The laminar flow will appear to come towards you, and though slower recede behind you.

In real wind, regardless of velocity, the tailwind and it's laminar flow, will move away, ahead of you, and come from behind you. You are in the wind. You entering an existing flow.
The laminar flow does no accumulate. The average flow is still in the direction of the wind. The mass per unit time is the same. Slower air, higher density, same mass/time as the real wind. (Close enough)

 

[humber]

Guys, it should be painfully obvious by now that humber is sincere in his misunderstanding.

Only the first part, Mender.

To change his world view would indeed be as "earth-shaking" as convincing a flat-earther that the world is round. It may not be possible for that to happen. I know I'll get some flack for my next statement but I see humber as intellegent (certainly word-wise) but not capable of getting this.[/QUOTE

I could, "shake your Earth", Mender, but that is not is what at stake. When you realise what is actually happening on the belt, you may be somewhat enlightened, but that will be tempered by chagrin. I believe you are all resisting that outcome.

 

[humber]

I have to go now, but if you will please think about what I have said. Later, I will pose a problem to you concerning the operation of a belt-powered vehicle.
No box cars, just simple mechanics.

 

[Dan O.]

Not faster, no. Take the position relative to the ground. The belt moves right to left. If the cart advances up that belt it moves left to right. That reveals the differential velocity of belt and cart. The laminar flow moves with the belt, Forget the profile, there is a flow, and that flow can be "backwards" relative to the forward motion of the cart on the belt.
You know that it is possible to translate these velocities back to the belt, so it is arithmetically sound.


Again,not faster.



It's not! That's the point. From that position you describe, increase your velocity so that you move up the belt. The laminar flow will appear to come towards you, and though slower recede behind you.

In real wind, regardless of velocity, the tailwind and it's laminar flow, will move away, ahead of you, and come from behind you. You are in the wind. You entering an existing flow.
The laminar flow does no accumulate. The average flow is still in the direction of the wind. The mass per unit time is the same. Slower air, higher density, same mass/time as the real wind. (Close enough)

We need to keep going through this until humber gets it right.

Humber, on the treadmill, when the difference between the velocity of the air and the velocity of the belt is to the right at 10 mph, where is the air moving to the left faster than the belt? On the road, when the difference between the velocity of the air and the velocity of the road is to the right at 10 mph, where is the air moving to the left faster than the road?

 

[mender]

When you realise what is actually happening on the belt, you may be somewhat enlightened, but that will be tempered by chagrin. I believe you are all resisting that outcome.

I asked about your interpretation of what is happening with the cart on the belt quite a while ago, and had you confirm that what I wrote was essentially correct at that time. Since you haven't changed how you are thinking the cart works, I doubt that you have more to offer that will be convincing. But go ahead; I'm sure "all" are waiting for a comprehensive and enlightening explanation.

Please try to remember that I'm not blindly accepting anything by anyone. I have a prop cart and a treadmill and have been conducting my own testing. I offered to do unbiased testing for you but haven't heard any tests from you, so I did some of my own. I have already tested several of your "concepts" to make sure that I haven't missed a possible explanation. Unfortunately, tests to prove your points have been negative, and have proven the opposite of what you claim.

I'll pick one of your "concepts", the inherent balance that you say the cart is forced into by the treadmill test. The balance that you claim is so powerful is not there. Having the cart remain on the belt for an length of time requires everything to set very carefully and that condition is actually quite delicate. There is a very small window of belt speed that the cart will be close to that balanced condition.

Which brings me to another of your contentions: the wheels slipping/cart losing traction/being lifted by a laminar airflow, etc. The consequence of reduced traction by any of the mentioned causes is testable and shows the same result. The cart slows down wrt the ground/belt. Remember two of the counter forces acting on the cart, thrust from the prop and induced drag from the wheels to provide that thrust. Remove one or even reduce one by a small amount and the cart either moves forward or backward. If the wheels slip, the cart moves back with the belt because the wheels have to transmit power from the moving ground/belt to the prop (tested). The slipping causes a loss of thrust which is more than the loss of drag from the slipping. Sounds wrong but it is true because the cart always has rolling resistance as well as the induced drag from turning the prop.

Without the prop, the cart has a specific rolling resistance (tested). When the wheels are turning the wheels drag (tested) and the prop provides thrust (tested). At a high enough belt/ground speed, there is enough energy in the wind (real/belt) that can be harnessed to spin the prop and overcome the "base" rolling resistance of the cart at that speed and the cart will move as fast as the air around it (tested). When the amount of energy in the wind is higher (speed difference between the ground and air is increased) or the induced drag is reduced for the same thrust (higher efficiency of the prop /drive system) or the rolling resistance of the cart is reduced (better bearings on the axles), the thrust from the prop will make the cart go faster still (tested). The final speed is determined by the amount of rolling resistance of the cart vs the power of the wind (not tested or quantified by my tests yet - see Ynot's turntable tests and Jack Goodman's outdoor test for testing so far).

Of course, that's only what my testing and JB's testing and spork's testing and Jack Goodman's testing shows, and Mark Drela says and spork says and ... so on. There is a growing mountain of evidence and explanations that support my view. I have yet to see any evidence that supports your view. So far there is nothing to resist.

 

[humber]

"

I asked about your interpretation of what is happening with the cart on the belt quite a while ago, and had you confirm that what I wrote was essentially correct at that time. Since you haven't changed how you are thinking the cart works, I doubt that you have more to offer that will be convincing. But go ahead; I'm sure "all" are waiting for a comprehensive and enlightening explanation.

Can't agree. Let them eat cake.

Please try to remember that I'm not blindly accepting anything by anyone.

Good, then you have taken my meaning regarding the value of authority.

I have a prop cart and a treadmill and have been conducting my own testing. I offered to do unbiased testing for you but haven't heard any tests from you, so I did some of my own. I have already tested several of your "concepts" to make sure that I haven't missed a possible explanation. Unfortunately, tests to prove your points have been negative, and have proven the opposite of what you claim.

Yes, I know, thanks. You could have told me that you have tested some ideas! I made a rudimentary belt from an electric drill, some plastic waterpipe and vinyl sheet. I find mine works.

I'll pick one of your "concepts", the inherent balance that you say the cart is forced into by the treadmill test. The balance that you claim is so powerful is not there.

Mender! I have said that there is almost no force, how many times?

Having the cart remain on the belt for an length of time requires everything to set very carefully and that condition is actually quite delicate. There is a very small window of belt speed that the cart will be close to that balanced condition.

That is in complete agreement with what I have said. The system works only between certain levels of friction. This I have also stated ad nauseaum!!!.
I told Spork that is the case, you must "fit it" to make it work! You have made the same mistake, it seems.
It is indeterminate, yes. About the "flywheel" . Without enough friction, it may become unstable. I described this as minimum "system Q" as a simplification. See? All been said, but not heard.

Which brings me to another of your contentions: the wheels slipping/cart losing traction/being lifted by a laminar airflow, etc. The consequence of reduced traction by any of the mentioned causes is testable and shows the same result.

Things are not that black and white. It is possible that the presence of the laminar flow broadens the working range, but I suspect it narrows it.

The cart slows down wrt the ground/belt. Remember two of the counter forces acting on the cart, thrust from the prop and induced drag from the wheels to provide that thrust.

Inconsistent. Now there is force at windspeed.

Remove one or even reduce one by a small amount and the cart either moves forward or backward.

As I said it would.

If the wheels slip, the cart moves back with the belt because the wheels have to transmit power from the moving ground/belt to the prop (tested).

I'm batting 100.

The slipping causes a loss of thrust which is more than the loss of drag from the slipping. Sounds wrong but it is true because the cart always has rolling resistance as well as the induced drag from turning the prop.

It also has momentum stored in the prop. That is the only energy source that is not immediately dependent on friction to the belt. That breaks the wheels-needs-prop-needs-wheels cycle.

Without the prop, the cart has a specific rolling resistance (tested).

Vague. The prop modifies the behaviour. The rolling resitance is not the same as the static resistance, which is again different when balance is achieved.
I though of asking for this test, but it would also be necessary to turn the cart around, for example, to make sure that the applied force (a spring balance perhaps) was not unduly influencing the result.

When the wheels are turning the wheels drag (tested) and the prop provides thrust (tested). At a high enough belt/ground speed, there is enough energy in the wind (real/belt) that can be harnessed to spin the prop and overcome the "base" rolling resistance of the cart at that speed and the cart will move as fast as the air around it (tested).

I suppose it would. Though "energy"?

When the amount of energy in the wind is higher (speed difference between the ground and air is increased) or the induced drag is reduced for the same thrust (higher efficiency of the prop /drive system) or the rolling resistance of the cart is reduced (better bearings on the axles), the thrust from the prop will make the cart go faster still (tested). The final speed is determined by the amount of rolling resistance of the cart vs the power of the wind (not tested or quantified by my tests yet - see Ynot's turntable tests and Jack Goodman's outdoor test for testing so far).

That a prop cart can be built or improved by the means you described, is not in question. The treadmill is.
As for the remainder, I cannot say. Could be either way. Ynot's system has tether, that is quite another matter. (Why do you need a tether?)

Of course, that's only what my testing and JB's testing and spork's testing and Jack Goodman's testing shows, and Mark Drela says and spork says and ... so on. There is a growing mountain of evidence and explanations that support my view. I have yet to see any evidence that supports your view. So far there is nothing to resist.

I see that you didn't take my meaning regarding authority.

Mark Drela seem to think that a cart can easily go as fast as wind, without hobos in boxcars. All objects blown by the wind, reach windspeed. What is your point?

Sorry, but I would describe your evidence as Phyrric, Mender.

You do need my explanation, after all.

 

[Dan O.]

Humber, you have failed the equivalency test through forfeiture yet again. If you can't answer the simple questions, everything else you have to say is make believe and doesn't belong in a science thread.

Everybody else agrees that there is no situation involving the wind, the cart and the surface the cart is running on that will make a significant difference in the behavior of the cart depending on whether the surface is a road with a steady breeze or a moving treadmill belt in a room of still air.

Every attempt of yours to show a difference only shows your failure to understand. Stopping the cart with respect to the road in one case and stopping the cart with respect the air in the other case is not the same situation. If you change the situation, we all expect to see differences.

The equivalent action to stopping the cart on the road is to stop the cart with respect to the belt so that the cart is moving backwards in the room and with respect to the air.

The equivalent action to stopping the cart with respect to the air in the room is to stop the cart with respect to the air over the road. To do that, you would need to drive up to the moving cart in another vehicle, set the cruse control to the fixed speed of the wind then attach to the cart.

Humber, are you physically incapable of seeing this equivalence? Nobody else is having a problem with it. Do you honestly believe that you are the only one that can see the truth? Do you think we are all cohorts in this elaborate conspiracy to try and confuse you?

 

[Brian-M]

It seems to me, that the only connection, is that it allows it to be said that "you can't tell" one wind condition from another. But you can.
If you can simply accept that frames have nothing to do with the treadmill, and just look at it as a machine, (which is what it is) you will realise that the model is nothing like it claims to be, and some claims are even impossible.

In the treadmill example, there is a relative difference in velocity between the air and the surface the cart is on.
In the road example, there is a relative difference in velocity between the air and the surface the cart is on.

In both cases, when the cart is at the same velocity as the surface it is on, the the air is moving forward relative to the cart.
In both cases, when the cart is at the same velocity as the air, the surface it is on is moving backwards relative to the cart.

I can't see any difference between these two examples. The forces acting on the cart from the air and the surface it is on are the same either way.

If you have reason to believe otherwise, then explain it to us clearly, concisely and unambigiously.
Your attempts to explain it to us so far have being vague, confusing and often contradictory.

As for frames having nothing to do with it, frames of reference are just a way of looking at the same situation from a different perspective. You can look at any situation from any arbitrary frame of reference. Different frames of reference don't change the outcome or interactions. Choosing the most convenient frame of reference just makes it easier to understand what's going on.

If you want to look at everything from the frame of reference of an observer stationary relative to the closest portion of the earth's surface, that's fine. Just remember, that the same outcome occurs no matter what frame of reference you work out the results from. So if your results contradict the results that someone has come up with using a more convenient frame of reference, then the chances are that your results are wrong.

 

[Brian-M]

The laminar flow is in the opposite direction of the tailwind.
From the side of the treadmill, the laminar flow moves right to left with the belt. while the air above is stationary. Arithmetically translate that to beltspeed, and the laminar flow will remain in opposition to the tailwind. It is not consistent with real wind. I have more.

From the side of the treadmill, the laminar flow loves right to left slower than the belt. This means that from the perspective of someone on the belt, the laminar flow is moving in the same direction as the tail-wind, only slower.

Exactly like the "real" wind. There is no difference.

 

[Brian-M]

Now is it not absolutely so, that if a boat has no velocity relative to the water, then every molecule must be in some kind of time warp? How can that not be the conclusion? They cannot move relative to each other without moving relative to the boat. That is just impossible! Why don't all rivers do this, even if there are no boats in it? Don't evade the question!

If the boat has no velocity relative to the average velocity of the water, there is no time warp needed. The average velocity of the molecules average out to the same velocity as the boat.

If you put a boat in a lake where the water is still, the molecules of water are still moving relative to the boat, they just average out to zero.

I don't see what you find so difficult to understand about this.

Sure some water molecules travelling slower than average will bump into the front of the boat, but other water molecules travelling faster than average will also be bumping into the back of the boat. This alll averages out to average velocity.

 

[jjcote]

In real wind, regardless of velocity, the tailwind and it's laminar flow, will move away, ahead of you, and come from behind you.

Outdoors, "real wind", no treadmill.

Windspeed 10 m/s, north to south. Wind gradient due to laminar flow causes the wind 10 cm above the ground to be 5 m/s, north to south. Sail cart (no props or anything, just a simple sail) is heading south, blown by the wind, at 9 m/s.

Okay with that example?

The cart overall feels a 1 m/s tailwind, right? What does it see if you look down at ankle level? A 4 m/s headwind.

Same as on the treadmill, in terms of direction.

 

[Brian-M]

On the treadmill belt in still air...

From that position you describe, increase your velocity so that you move up the belt. The laminar flow will appear to come towards you, and though slower recede behind you.

On the road with a "real" tail-wind...

From that position you describe, increase your velocity so that you move up the road. The laminar flow will appear to come towards you, and though slower recede behind you.

In the "real" wind the laminar flow is moving slower than the wind. So, as you approach wind speed, the laminar flow appears to be moving in the opposite direction.

Just like on the treadmill belt.

There is no difference.

 

[Brian-M]

Humber, one of the reasons why we're not particularly inclined to accept your unsupported assertions about the laws of physics is because of the implications of what you are saying.

What you're saying amounts to it being possible to determine whether on not a system is in motion with simple mechanical experiments.

For example, the treadmill is the same as putting the cart on the back of a long truck or train and driving the truck/train through still air.

Your claim that this won't affect the cart the same way as a "real" wind would means that it would be able to tell whether or not the truck/train was moving through still air, or stationary in moving air, by observing the behaviour of the cart.

Your claim that someone jumping straight up in an enclosed box cart travelling at a constand velocity wouldn't land on the same spot he started from (unless he was quick) provides another simple mechanical test to tell whether or not the system is moving.

So does your claim that someone with a parachute and roller-skates would reach air-speed on a treadmill, but not on the ground.

As do your claims that boats/balloons can't reach water/wind speed when the water/wind is moving (but can when the water/wind is still).

Almost everything you say would make it possible to tell whether or not a system is moving with simple mechanical experiments.

These claims go against established knowledge of physics.

You repeatedly assert that this information can by found in any textbook on the subject, yet you never provide links or quotes to support your views or provide a clear explaination of what you are trying to say.

It's not hard. This morning, for example, I flipped through Feynman's "Six Not-So-Easy Peices" and found this...

If we substitute this transformation of coordinates into Newton's Laws we find that these laws transform to the same laws in the primed system; that is, the laws of Newton are of the same form in a moving system as in a stationary system, and therefore it is impossible to tell, by making mechanical experiments, whether the system is moving or not.
The principle of relativity has been used in mechanics for a long time. It was employed by various people, in particular Huygens, to obtain the rules for the collision of billiard balls, in much the same way as we used it in Chapter 10 to discuss the conservation of momentum.

Did you get that?

the laws of Newton are of the same form in a moving system as in a stationary system, and therefore it is impossible to tell, by making mechanical experiments, whether the system is moving or not.

So, on one hand we have one of the most highly respected physicists of the 20th century, and on the other hand we have you, an anonymous internet user.

Do you begin see why your unsupported, poorly explained assertions don't seem too convincing to us?

Try looking in one of those physics books you claim support your views, and provide us with actual quotes of statements that do.

If you can find any.