Merged DDWFTTW in a “Real” Wind

[A.T.]

You can say the ground has kinetic energy,
...
I still disagree that vehicles can be powered by energy from the ground.

That's a serious disconnect you have there. Maybe you should go argue that with yourself first.

People can get into a muddle when you try to use different reference frames that only confuse the situation.

If you find reference frames confusing, then it is useless dicussing frame dependent concepts like energy with you.

 

[sol invictus]

I do agree that energy is frame dependent, just as velocity is. I still disagree that vehicles can be powered by energy from the ground.

You agree that vehicles can be powered by a moving air mass, but not by a moving earth mass. That's an odd point of view.

Yes, that is a way of looking at things, but what purpose does it serve when you know beyond any doubt that the cart in this case is being powered by the wind?

Wind is the relative motion between air and ground. In a frame where the ground is at rest, wind is the motion of air. In a frame where the air is at rest, wind is the motion of ground.

Why do you want to use a reference frame that does not correctly describe what is happening?

All reference frames can be used to correctly describe all events.

 

[profpangloss]

That's a serious disconnect you have there. Maybe you should go argue that with yourself first..

No disconnect at all. If two vehicles are travelling along at 50 mph, one directly in front of the other and in the same direction, they have no kinetic energy relative to each other. (Assume they are the same mass). Now the lead vehicle jams on the brakes, so it gains kinetic energy with respect to the vehicle right behind it. Do you imagine that the second vehicle can be powered by the kinetic energy that now exists betwen the two? Maybe if it slams into the vehicle ahead at full speed, the second vehicle can go faster (maybe some pieces of it). The ground is not going to provide energy to vehicles moving on it, in any frame. It always acts to work against the motion.

If you find reference frames confusing, then it is useless dicussing frame dependent concepts like energy with you.

That isn't what I said, I am not confused but it seems some people want to make it confusing. Maybe they are trying to hide something?

 

[humber]

There you go again with the insults, Humber


It's dreadfully telling that, when asked to provide evidence that you can actually, you know, do the maths, you default to insulting those who ask.

"it's telling" is a hackneyed rhetorical device, frequently employed to suggest superior knowledge or insight. It so often fails.

 

[jadebox]

No disconnect at all. If two vehicles are travelling along at 50 mph, one directly in front of the other and in the same direction, they have no kinetic energy relative to each other. (Assume they are the same mass). Now the lead vehicle jams on the brakes, so it gains kinetic energy with respect to the vehicle right behind it. Do you imagine that the second vehicle can be powered by the kinetic energy that now exists betwen the two? Maybe if it slams into the vehicle ahead at full speed, the second vehicle can go faster (maybe some pieces of it). The ground is not going to provide energy to vehicles moving on it, in any frame. It always acts to work against the motion.

Your "two vehicles [...] travelling along at 50 mph" analogy doesn't have any relationsihip to the situation.

I think you're getting confused by the idea of the ground moving.

If it makes it easier for you to understand, try replacing "the ground" with "a river." It's not counterintuitive to think of a river as moving and powering a vehicle. In the case of the down-wind cart you can replace the cart with boat and think of the air as tending to hold the cart in place while the river flows below it.

A real-world example of the ground providing energy to vehicles moving on it are the breaking generators that some electric vehicles have. They convert the kinetic energy of the car's motion, relative to ground, back into eletricity.

-- Roger

 

[humber]

Yes. I agree in this case the treadmill is the source of energy.







I don’t know of any examples where the road is a source of energy for vehicles travelling on it. By road I mean that it is part of the planet. The world is moving all the time but because of gravity everything including the atmosphere moves with it, except for local variations called winds that are not related to planet rotation. If everything moves with it, it cannot be source of energy to anything. This is different from the treadmill because gravity tries to hold things in place while the tread surface moves laterally to the force of gravity. I see where this case can be exploited to get energy to drive things like a cart on the treadmill. I don’t see similar situation with the road, which is the whole world.




Sorry, but as I see it they are two different cases for the reason I have given.

Correct, and quite obviously so, but Spork and his followers think that changing the (sentient) observer's point of view, changes physical reality.
The call that "frames of reference", Galilean Transformation etc.
They are quite fixated with that idea, and see it as insightful.

So that you know, they see a runner on a treadmill as being exactly the same as a runner on the road. Hilariously, the absence of motion with the air is explained by there being a tailwind, and the runner is at the speed of that tailwind.

 

[profpangloss]

You agree that vehicles can be powered by a moving air mass, but not by a moving earth mass. That's an odd point of view.
.

Odd to you perhaps, not to me. But try to be a bit more specific, please. I am not talking about a moving earth mass, like a landslide here, but the moving earth! That is a significant difference since the gravitational force of the earth moves everything along with it. If something is to move independently of the moving earth, it must have a source of energy other than the earth itself, something like a wind or an engine. The earth is not going to assist something in moving with respect to the earth itself.

Wind is the relative motion between air and ground. In a frame where the ground is at rest, wind is the motion of air. In a frame where the air is at rest, wind is the motion of ground..

Once again, please don't say the ground, when you mean the entire earth. The ground may be a conveyor belt and that is the entire point; the road cannot be a conveyor belt because it is the earth itself and they are not the same.

All reference frames can be used to correctly describe all events.

Yes but some frames are more convenient and make more sense than others. You don't use the frame of the moon to navigate your car out of the driveway and over to Hooters, now do you? Or maybe you do?

 

[semper]

No disconnect at all. If two vehicles are travelling along at 50 mph, one directly in front of the other and in the same direction, they have no kinetic energy relative to each other. (Assume they are the same mass). Now the lead vehicle jams on the brakes, so it gains kinetic energy with respect to the vehicle right behind it. Do you imagine that the second vehicle can be powered by the kinetic energy that now exists betwen the two? Maybe if it slams into the vehicle ahead at full speed, the second vehicle can go faster (maybe some pieces of it). The ground is not going to provide energy to vehicles moving on it, in any frame. It always acts to work against the motion.

That isn't what I said, I am not confused but it seems some people want to make it confusing. Maybe they are trying to hide something?

Hi profpangloss, perhaps it would be helpful to consider a different scale planet and car scenario. What if your planet had a similar mass to your car, and was sized so that it could only just fit the car on it. How does driving work on this type of planet, in particular, consider the momentum conservation issues. Take a look at how the energy gets distributed too.

 

[profpangloss]

Your "two vehicles [...] travelling along at 50 mph" analogy doesn't have any relationsihip to the situation.

I think you're getting confused by the idea of the ground moving.

If it makes it easier for you to understand, try replacing "the ground" with "a river." It's not counterintuitive to think of a river as moving and powering a vehicle. In the case of the down-wind cart you can replace the cart with boat and think of the air as tending to hold the cart in place while the river flows below it.

-- Roger

If I am going to replace the ground with a river, I may as well replace it with a treadmill! That is exactly what I am debating against! The ground is the earth itself, and it does not run under things like a treadmill or a river. Roads don't flow along giving up energy! To move over a road a vehicle must have a source of energy and it cannot be the road itself. As long as you think of the ground as a river, it will be you that is confused, not me.

 

[profpangloss]

Hi profpangloss, perhaps it would be helpful to consider a different scale planet and car scenario. What if your planet had a similar mass to your car, and was sized so that it could only just fit the car on it. How does driving work on this type of planet, in particular, consider the momentum conservation issues. Take a look at how the energy gets distributed too.

Again, this is exactly what I am arguing against. If you are going to do that, shrink the world down to the size of a treadmill, you are changing the argument entirely. I am talking about a road on this planet and what it takes to move a cart along that road. Some here seem to think the road itself can power the car to run along it. I say that is totally fantastically wrong.

 

[A.T.]

We're all starving for adult conversation, and this seemed like a good opportunity.

Get your Harold radar repaired, spork.

 

[profpangloss]

Correct, and quite obviously so, but Spork and his followers think that changing the (sentient) observer's point of view, changes physical reality.
The call that "frames of reference", Galilean Transformation etc.
They are quite fixated with that idea, and see it as insightful.

So that you know, they see a runner on a treadmill as being exactly the same as a runner on the road. Hilariously, the absence of motion with the air is explained by there being a tailwind, and the runner is at the speed of that tailwind.

I would like to know why they need to resort to such a device to explain a simple cart? That alone makes me very suspicious that all is not what it seems here.

 

[jadebox]

Correct, and quite obviously so, but Spork and his followers think that changing the (sentient) observer's point of view, changes physical reality.

profpangloss,

humber has previously argued that changing an observer's point of view actually does change the physical reality of the system. Now, he's claiming that others are making the same mistake. I hope you'll understand that the treadmill is a good analogy of the cart in the wind. It doesn't matter if the cart is moving relative to the road or if the road is moving relative to it. Both situations are the same.

I would like to know why they need to resort to such a device to explain a simple cart?

The way the cart works isn't simple and it's counterintuitive. If you're willing to listen, there are people here who can explain how it works. But, you will have to accept that your preconceptions about some things may be wrong.


-- Roger

 

[profpangloss]

Get your Harold radar repaired, spork.

Care to let us all in in the cryptic remark?

 

[profpangloss]

profpangloss,

humber has previously argued that changing an observer's point of view actually does change the physical reality of the system. Now, he's claiming that others are making the same mistake. I hope you'll understand that the treadmill is a good analogy of the cart in the wind. It doesn't matter if the cart is moving relative to the road or if the road is moving relative to it. Both situations are the same.

-- Roger

I have explained why I believe they are not the same. You have only asserted that they are. Can you do better than that? Convince me.

 

[humber]

You agree that vehicles can be powered by a moving air mass, but not by a moving earth mass. That's an odd point of view.

So I was right. Adoption of Steve Smith's "explanation" of extraction of energy from the slowing of the apparent wind, is a smoke screen to mask the initial claim that the ground powers the cart. A stop-gap measure, until the proposed wind power generation project - which must be underway to some degree, or Spork would have denied it - will be the vindication of that crackpot claim.

Wind is the relative motion between air and ground. In a frame where the ground is at rest, wind is the motion of air. In a frame where the air is at rest, wind is the motion of ground.

Wind is the motion of the atmpsphere due heating by the sun. Apart from some extraneous effects, it does not depend upon relative motion with respect to the ground. To say that from the "frame of the air" the "ground moves", is a major error. Imputing an observer, said to be at rest with the air, does not make that observer or the air at rest.

All reference frames can be used to correctly describe all events.

Not as you do it. Moving the frame of reference, does not make that frame, the rest frame. Once a rest frame is declared, then observations made by any observer, are made relative to that rest frame, and not relative to the observer. A transform unites the two. A new transform is not made for each subsequent observational frame.

 

[A.T.]

I am not confused

You are obviously very confused about reference frames:

Why do you want to use a reference frame that does not correctly describe what is happening?

 

[Modified]

To move over a road a vehicle must have a source of energy and it cannot be the road itself.

To move on a treadmill, a vehicle must have a source of energy, and it cannot be the treadmill itself.

To move on a river, a vehicle must have a source of energy, and it cannot be the river itself.

These statements are equivalent to yours.

I would like to know why they need to resort to such a device to explain a simple cart?

It hasn't been needed to explain it at all. For testing something that is moving at or very near wind speed, a treadmill is ideal. It provides a consistency in speed and direction of the wind that is difficult to get anywhere else. To anyone with a basic knowledge of physics, the carts tested on treadmills conclusively demonstrate dwfttw travel.

 

[A.T.]

Convince me.

Convince us

 

[A.T.]

Get your Harold radar repaired, spork.

Care to let us all in in the cryptic remark

My remark was directed at spork. Funny that you make 'blip'.