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

[humber]

greg:

humber:
This right here is the problem in a nutshell. The cart generates power based on teh difference between wind and ground. That difference is always the same, no matter how fast the cart is going.

The belt is the power for the wind. That is not equivalent to your scenario.
Also, if I built a generator based upon the design of the cart, (I can do that) you are suggesting that I can generate power at windspeed.

If the cart only generated power based on teh wind, like it used a simple sail and the wheels were freely rolling, then you'd be correct: It would only extract power as long as it was going slower than teh wind.

You need to show that it is not a sail. It is not enough to behave like sail, but be distinguishable from a sail. It looks to me to be like a sail.

But the cart doesn't work that way. It extracts power based on teh difference between air and ground and that difference is always the same. So the power available is independent of teh cart velocity.

Evidence suggests otherwise. Where is the ground if it not the belt?

As long as you think the power is a function of teh wind only, rather than a function of the difference between wind and ground, you will struggle with this.

There is no struggle. There is no evidence that you are correct, Greg.

 

[humber]

I think there is a problem with your approach here H'ethetheth. As previously shown:

Humber + Numbers = Gibberish

Now, solve for X. Do you see?

....or the reaction to bluff or straw man.

 

[Clive]

I'm waiting for the "reveal". I'm currently putting my money on Humb being a creation of Humber, and then in turn, Humber being a creation of spork's. Or perhaps JB is Humb and spork is Humber? In any case, I'm sure we've all been taken for a ride.

 

[humber]

Y'know, props are funny. What's the drag (in the forward direction) of a spinning prop? That is, how much harder is it to pull a cart forward if it has a spinning prop on it, compared to having no prop at all (or a spinning stick, or a rag, or whatever)? It's weird, you don't have to pull harder on the cart when you add a spinning prop. In fact, you have to restrain it from moving forward. What a strange thing, it seems to have negative drag, at least over some limited speed range. So how is it that removing the prop eliminates the drag of the cart?

You can wikk that. It is a common enough phenomenon. Sometimes the result of cavitation.

 

[John Freestone]

Or your comprehension is disturbingly bad.

ETA:
You could propose a system of measuring the treadmill cart's KE

Try measuring the cart's mass and velocity and punch the numbers into that equation, oh, it's on the tip of my tongue...

Oh I forgot, you don't know what velocity is.

Which way does a piece of paper bend when you wave it through the air?

 

[GregLondon]

It looks to me to be like a sail.

But it isn't. that's why you're not seeing it.

Also, if I built a generator based upon the design of the cart, (I can do that) you are suggesting that I can generate power at windspeed.

Sure. If you allow me to use generators that are as efficient as propellers (80%) while having as little friction as the propellers. Assume you've got relatively linear generators for the speeds/RPM's we're talking about. Say, they're both geared to generate 1 watt per mph. And I think we can translate the propeller/wheel cart to your power concerns.

This is all really metaphorical because I don't know if generators and electric motors have the efficiency and low friction needed to work in such small windspeeds without needing a 20 foot prop or something crazy.

build a platform with four wheels. tie a generator to one wheel. Tie an electric motor to another wheel. on the platform, build a little tower, mount a propeller on the tower and put a generator on that tower. The propeller is not mechanically connected to the wheels. Wire the two generators so that they can dump both of their power outputs into the motor.

Get a 10 mph tailwind. Start with the cart at rest. How much power is available to the cart? 10 watts.

10 watts goes into the motor and accellerates the cart to 1 mph.

At 1 mph, how much power is available to the cart? 9 watts from the wind generator and 1 watt from the wheel driven generator=10 watts. 10 watts goes intothe motor and accelerates the cart to 2 mph.

At 2 mph, how much power is available tot he cart? 8 watts from the wind generator and 2 watts from teh wheel generator=10 watts. 10 watts goes into teh motor and acceleratos the cart.

This continues until the cart is going 10 mph in a 10 mph wind. How much power is available?

0 from the wind generator, 10 from the wheel = 10 watts. 10 watts goes into the motor accelerating the cart to 11 mph.

at 11 mph, how much power is available? well, the windmill generator is probably generating negative current and the wheel generator is generating 11 watts, so it works out to be 10 watts, whcih accelerates the cart.

When does the cart stop accellerating? The answer has nothign to do with the speed of teh wind, because you have 10 watts no matter how fast the cart is moving. The cart stops accelerating when it reaches whatever speed causes friction to dissappate 10 watts of power. At that point, whatever the velocity may be, the cart hits steady state.



If you just had a cart with a free-spinning propeller witih a generator attached to the propeller, then you'd top out somewhere below the speed of teh wind because the prop is your only source of power.

But you also get power from the wheel.

Not that I'd recommend building a cart from generaotrs and electric motors, but its a way to try and show you where you're missing where the power is coming from.

It's not just the wind. Its the wind and the wheel.

 

[Furcifer]

It is closed for all the purposes of measurement. Why not?

I'm not sure. I don't think there is a simple answer.

My best guess? Pressure. Air on the back of the prop, compressed by the tailwind (or "gathered" there), essentially adds mass to the "system" (m*a/unit area), which accounts for the increase in velocity. Depending on the pitch of the prop and it's surface area there should be a finite amount of air added into the "system".

 

[John Freestone]

You have not manged to demonstrate how your fisg tank is like the treadmill.
you saud you could.

I think you'll find that you suggested replacing the treadmill with a fishtank months ago.

 

[GregLondon]

Humb being a creation of Humber, and then in turn, Humber being a creation of spork's. Or perhaps JB is Humb and spork is Humber? In any case, I'm sure we've all been taken for a ride.

The possibility crossed my mind.

 

[humber]

I think you'll find that you suggested replacing the treadmill with a fishtank months ago.

Not all sentences containing 'fishtank' have the same meaning.

 

[H'ethetheth]

100% Evasion.

Oh humber, you do go on!
I don't think even iron is this irony.

You have not manged to demonstrate how your fisg tank is like the treadmill.
you saud you could.

I have named several essential respects in which the two are similar. Your failure to understand is not my fault.

(1) You claim 15 mistakes in my understanding of relative motion.

...in that post alone, yes.

Please justify one of them where your conclusion contradicts mine.

You should read the rest of the post if you want to know. In fact, I asked you for numerical estimates several times but I see you're not going to talk numbers.
I'll humour you though:

The latter [displacement] appears in all frames, meaning that it is displacement and not velocity increase. It has essentially no motion.

First of all, a displacement appearing in all frames is hard to parse. Either it is in a certain position, meaning in all frames it has a different position. Or it is a changes position over time, meaning that it is moving. Seeing how velocity is relative to a chosen reference frame, no motion can appear in all reference frames.
The second sentence has no physical meaning. Something cannot "not have" motion. It's like saying, this object is not to the left. It depends on who you ask, because guess what...

motion is relative.

(2) Why a human runner on a belt is like a cart.

Okay, you ask for the answer, and you'll get the same one again: Both represent the dynamics of a system that normally moves with respect to the ground; both transform all interactions so that the subject is no longer moving relative to a comfy chair, from which they can then be studied.

(3) You also failed to address the matter of how wind and a belt are needed to generate the correct boundary layer.

No, I'm sorry, you simply failed to recognize the answer because it does not fit with your muddled conception of motion.

Oh and as a bonus, I missed the comment where you said:

Please explain why it is said, and how it is like the fish tank you said was equivalent.

If you would understand what I'm telling you, you would know that I never claimed they are equivalent. I've claimed they are similar in many ways.

 

[jjcote]

You can wikk that. It is a common enough phenomenon. Sometimes the result of cavitation.

Ignoring, of course, the little detail that cavitation can't occur in air.

Who ever is keeping the bizarrely misused buzzwords list, with terms like "adiabatic", please add "cavitation"

 

[John Freestone]

Greg, I wonder if you'd mind using the quote button a bit more. It keeps the poster's name and a link to their post in the quote tags, which helps to avoid confusion. I like to know who said what and sometimes go back to check out the whole thing. Pretty please? You can toggle the multi-quote buttons to respond to several posts at once - just select the posts and the buttons will get highlighted, then click Quote on another, or one of them, it doesn't matter which. You can do this and navigate to different pages, and I think they get inserted in the order you select them.

Up to you, of course, just a friendly request. Sometimes it's good to be able to click back several posts to see where some odd idea started, and round here, there are quite a few odd ideas. Welcome to the forum, by the way.

 

[John Freestone]

Not all sentences containing 'fishtank' have the same meaning.

That's exactly what I said.

 

[humber]

But it isn't. that's why you're not seeing it.

I see it, But is wrong. I mention the maximum power theorem, something that applies to all power transfer, but you still maintain an exemption for chutes and carts. That makes no sense.

Sure. If you allow me to use generators that are as efficient as propellers (80%) while having as little friction as the propellers.

Quite possible. But that does not matter because the power comes from the motor. If I put in 100W and get out 101W, then I am ahead.
This is what you are suggesting, but more so.

Assume you've got relatively linear generators for the speeds/RPM's we're talking about. Say, they're both geared to generate 1 watt per mph. And I think we can translate the propeller/wheel cart to your power concerns.

Watts are not measured by velocity.

[QUOTE}
This is all really metaphorical because I don't know if generators and electric motors have the efficiency and low friction needed to work in such small windspeeds without needing a 20 foot prop or something crazy.
[/QUOTE]
No need to worry about that. The cart extracts some, so a generator can too.

build a platform with four wheels. tie a generator to one wheel. Tie an electric motor to another wheel. on the platform, build a little tower, mount a propeller on the tower and put a generator on that tower. The propeller is not mechanically connected to the wheels. Wire the two generators so that they can dump both of their power outputs into the motor.

Get a 10 mph tailwind. Start with the cart at rest. How much power is available to the cart? 10 watts.

10 watts goes into the motor and accellerates the cart to 1 mph.

At 1 mph, how much power is available to the cart? 9 watts from the wind generator and 1 watt from the wheel driven generator=10 watts. 10 watts goes intothe motor and accelerates the cart to 2 mph.

At 2 mph, how much power is available tot he cart? 8 watts from the wind generator and 2 watts from teh wheel generator=10 watts. 10 watts goes into teh motor and acceleratos the cart.

This continues until the cart is going 10 mph in a 10 mph wind. How much power is available?

0 from the wind generator, 10 from the wheel = 10 watts. 10 watts goes into the motor accelerating the cart to 11 mph.

at 11 mph, how much power is available? well, the windmill generator is probably generating negative current and the wheel generator is generating 11 watts, so it works out to be 10 watts, whcih accelerates the cart.

When does the cart stop accellerating? The answer has nothign to do with the speed of teh wind, because you have 10 watts no matter how fast the cart is moving. The cart stops accelerating when it reaches whatever speed causes friction to dissappate 10 watts of power. At that point, whatever the velocity may be, the cart hits steady state.

I don't know. Too complicated and a lot of guessing? Power is not measured like that.

If you just had a cart with a free-spinning propeller witih a generator attached to the propeller, then you'd top out somewhere below the speed of teh wind because the prop is your only source of power.

What wind? The prop would not turn. The wheels turn the prop. How can that work?

But you also get power from the wheel.

A generator could be atached to the cart's prop shaft. And put on the belt. The output could be compared with the motor consumption, and the gain measured. A smaller version could be built. Think that will work?

Not that I'd recommend building a cart from generaotrs and electric motors, but its a way to try and show you where you're missing where the power is coming from.
It's not just the wind. Its the wind and the wheel.

That test would demonstrate that claim . Sounds to me like over-energy, though And I still can't measure the KE.

 

[humber]

That's exactly what I said.

Then it was not at all relevant

 

[humber]

Ignoring, of course, the little detail that cavitation can't occur in air.

Who ever is keeping the bizarrely misused buzzwords list, with terms like "adiabatic", please add "cavitation"

Try again. Air is a fluid. For someone who knew nothing about it, you seem to have learned a lot in a short time. I also said "sometimes".

 

[John Freestone]

Then it was not at all relevant

Oh. Sorry. I will observe you well, Master, to learn what is relevant.

I can't chat now, though. I want to get back to the cavitation discussion. I'm looking forward to learn about the air bubbles in the air, and how they affect the drag of a propeller.

 

[humber]

Oh. Sorry. I will observe you well, Master, to learn what is relevant.

I can't chat now, though. I want to get back to the cavitation discussion. I'm looking forward to learn about the air bubbles in the air, and how they affect the drag of a propeller.

Perhaps you need to look at the context of the reply. An aeroengineer should have seen that perhaps there is a distinction concerning negative drag, rather than your interpenetration. Negative resistance phenomenon occur in all sorts or things, including air.

 

[John Freestone]

Sounds to me like over-energy, though And I still can't measure the KE.

1. I think I can help you there. KE = mv²/2
2. What's over-energy?