Sum of energy not constant

[swansont]

1 hour ago, xyrth said:

It is not the same device, so, I think it could confuse people more. The first uses the gravity the second not. I found my mistake with the device with gravity, it is because I need to move up water when the water moves out from the bottom.

So you've simplified it, but it's still confusing as hell, as far as I'm concerned. I don't see any blue spheres, though I see purple ones. I don't see any springs. I don't see what you mean by "white inside" - inside of what? Then you say the white stays outside of the container. You say the volume of the container is constant, but your diagrams show it changing on length, and the strips are polystyrene. Do you explain this in any detail?

 

Why not model this with one strip, instead of a bunch?

[Strange]

6 hours ago, xyrth said:

I think, first, it is important to understand the animation: https://i.imgur.com/sgjch9Z.gifv

It shows a sheet of white corrugated paper attached to a blue board being distorted from a parallelogram to a rectangle. Maybe. Meanwhile a blue and a white rectangle change shape.

I have absolutely no idea what this is supposed to represent.

[xyrth]

I don't see any blue spheres, though I see purple ones: no purple is the axes of rotation of the white rectangles. The blue spheres are small, very small, like molecules of water, so imagine them with a radius of 1e-5 m for example, so the blue color IS the blue spheres. If I zoom in a lot, I could see the spheres.

 

I don't see any springs: true, I suppose the volume of the springs is 0, just because in the contrary it is difficult to draw and second, I would need to take in account these volumes, and I don't want because I don't need these volume for my calculations.

 

I don't see what you mean by "white inside" - inside of what?  Inside the container. I move out the parts of the white rectangles from the bottom, because the rectangles rotate around their axes (purple color) and I need to reduce their length. In the same time I move in the blue sphere (blue color).

 

Then you say the white stays outside of the container. You say the volume of the container is constant, but your diagrams show it changing on length, and the strips are polystyrene.: Yes, the volume of the container is constant, it passed from a parallelogram to a square, but even I move out the white parts of the rectangles, I move in the same volume of blue spheres.

 

Do you explain this in any detail? Yes, I can, just I don't know by what to start. I will try again.

 

It shows a sheet of white corrugated paper attached to a blue board being distorted from a parallelogram to a rectangle. Maybe. Meanwhile a blue and a white rectangle change shape. : I drew the side view of the device. At start, it is a parallelogram at final it is a square. If the depth of the container is 1m, then the volume of the container is always 1m³: I move out the white parts and I move in the blue spheres.

 

Thanks to try to understand me.

I calculate the sum of energy of a deformation of a device. That device is composed of :

1/ A container with a constant volume, at start the volume is a parallelogram and at final it is a square

2/ White rectangles that rotate around their axes (purple color) when the container is deformed. I reduce the length of the white rectangle because at start the length is 1.414m and at final it is 1m. At start, there is near 100 % of the volume of the container fulled of the white rectangles inside the container, at final there is only 70.1% of the volume of the container fulled with white rectangles. I drew only 18 rectangles, but I can have in theory 10000. I could explain why after.

3/ Blue spheres: so small that I can't draw, it is like molecules of water. I use small spheres to have the right to use the law of fluid under gravity (like gravity can do with water for example). But these spheres have no mass and no friction, because I want to calculate the exact sum of energy and I don't need a mass nor gravity.

4/ Springs with a volume of 0, so I can't drew them. Each spring is attached between the green line (the bottom wall) and a sphere. So if there is at final 1e10 spheres inside the container, there is 1e10 springs too. I took in account the potential energy of the springs. But like I want to have easier calculations, I took the springs with a constant force (doesn't depend of the length of the springs).  All springs HAVE the orientation of the lateral walls, they change when the device is deformed but at each time the orientation of the springs are the same, again to have the right to use the law of fluid under gravity.

The device is unstable, so I use an external device to control it, that external device count all the energies in/out, so the sum of these energies must be at 0 that I can't find.

 

Don't hesitate to ask me what is not clear.

Edited May 15, 2018 by xyrth

[Strange]

21 minutes ago, xyrth said:

I don't see any blue spheres, though I see purple ones: no purple is the axes of rotation of the white rectangles. The blue spheres are small, very small, like molecules of water, so imagine them with a radius of 1e-5 m for example, so the blue color IS the blue spheres. If I zoom in a lot, I could see the spheres.

The only blue I can see is the blue parallelogram behind the white stripes.

If the sphere are too small to see, why are they there?

22 minutes ago, xyrth said:

I don't see what you mean by "white inside" - inside of what?  Inside the container.

What container? There is no container in your diagram.

23 minutes ago, xyrth said:

Don't hesitate to ask me what is not clear.

Everything.

[xyrth]

What container: what contains the white rectangles, and the blue spheres. What is deformed from a parallelogram to a square

The only blue I can see is the blue parallelogram behind the white stripes: no it is blue spheres, imagine the blue spheres like a fluid. When the white rectangles rotate, there is more and more space between the white rectangles, I full that space with blue spheres (and the springs)

If the sphere are too small to see, why are they there? Because I need the pressure. The spheres are small but with a lot they occupy a volume: THE BLUE COLOR (like water). The blue spheres give the pressure on the walls.

 

[Strange]

20 minutes ago, xyrth said:

I full that space with blue spheres (and the springs)

You said there aren't any springs.

21 minutes ago, xyrth said:

The spheres are small but with a lot they occupy a volume: THE BLUE COLOR (like water). The blue spheres give the pressure on the walls.

So why not just use water?

21 minutes ago, xyrth said:

What container: what contains the white rectangles, and the blue spheres. What is deformed from a parallelogram to a square

So you haven't drawn the container. It is just implied by the sharp of the water.

So, in summary, you have a container which is full of water and white strips. The container can change shape but keep the same volume. When this happens, the white strips move with it but (somehow) change their length. Correct?

So the volume of the white strips must change (because they get shorter). So the level of water should drop (because there is less being displaced by the white strips). But that isn't shown in your diagram.

What is the point of all this?

You seem to have created something that is so complicated that (a) you can't correctly calculate what it does and (b) no one else can understand it.

 

[xyrth]

You said there aren't any springs: no I said the volume of the springs is 0, but each sphere has a spring, I use the spring to have pressure from the spheres.

 

So why not just use water?  When I use water the sum of energy is well at 0, but not when the source of attraction (the green line+springs) is attached on the device. At start, I found that device I calculated the sum of energy, and I didn't find 0 and after I tried to adapt it with water and gravity.

So you haven't drawn the container. It is just implied by the sharp of the water: it is a think black line around water, but it's true, the line is too thin.

So, in summary, you have a container which is full of water and white strips. The container can change shape but keep the same volume. When this happens, the white strips move with it but (somehow) change their length. Correct?  It is not water, it is spheres + springs. The white rectangles rotate around their axis (purple color) do you see them ?

So the volume of the white strips must change (because they get shorter). So the level of water should drop (because there is less being displaced by the white strips). But that isn't shown in your diagram: not water. The animation shows the blue spheres more and more between the rectangles no ?

What is the point of all this? I try to find my mistake

You seem to have created something that is so complicated that (a) you can't correctly calculate what it does and (b) no one else can understand it: no, with a lot of devices like that I found always the sum of energy at 0, not in that case. The device is not so difficult, and I calculated for a small angle of rotation, so it is linear. I gave the calculations for the cases 1 and 2 and I found the sum of energy at 0.

 

Edited May 15, 2018 by xyrth

[Strange]

3 minutes ago, xyrth said:

You said there aren't any springs: no I said the volume of the springs is 0, but each sphere has a spring,

If the volume of the springs is zero, then they don't exist.

4 minutes ago, xyrth said:

but not when the source of attraction (the green line+springs)

There are no green lines or springs in your diagram.

4 minutes ago, xyrth said:

So the volume of the white strips must change (because they get shorter). So the level of water should drop (because there is less being displaced by the white strips). But that isn't shown in your diagram: not water. The animation shows the blue spheres more and more between the rectangles no ?

You miss the point. The volume of the white strips decreases but the level of the blue doesn't. Why?

6 minutes ago, xyrth said:

What is the point of all this? I try to find my mistake

Well, good luck with that. Maybe someone here can make sense of this, but I certainly can't.

The only advice I can give is to start all your calculations again from scratch and maybe you will get the right answer. But it seems no one here (so far) can make any sense of your invisible spheres and zero-sized springs so you are on you own.

 

p.s. And learn to use the Quote function. It is quite hard to follow your responses. 

[xyrth]

Just now, Strange said:

If the volume of the springs is zero, then they don't exist.

It is a theoretical device. If you want, imagine the device with only one layer of spheres for the depth (perpendicularly to the screen), like that the springs can be outside. Just take in account the depth.

 

Just now, Strange said:

There are no green lines or springs in your diagram.

Oh yes, there is one, don't take the device with water, because the 2 questions were merged ! first with water+gravity, second with spheres+springs I add the image here again.

 

Just now, Strange said:

You miss the point. The volume of the white strips decreases but the level of the blue doesn't. Why?

There are white rectangles, no blue rectangles. Blue color is BLUE SPHERES like a fluid. But true, the blue spheres at bottom need to move out and move in again but I win/lost nothing because I need to increase the length of the springs to move in again. Even it could be a problem with a big angle of rotation, look at a small angle of rotation at start, imagine the angle like 0.0001° the energy won by the green line is twice than the springs lost and the volume of the blue spheres that move out is 0. I counted the potential energy of the springs.

[swansont]

20 hours ago, xyrth said:

I don't see any blue spheres, though I see purple ones: no purple is the axes of rotation of the white rectangles. The blue spheres are small, very small, like molecules of water, so imagine them with a radius of 1e-5 m for example, so the blue color IS the blue spheres. If I zoom in a lot, I could see the spheres.

OK, so why not just say it's some fluid? 

20 hours ago, xyrth said:

 

I don't see any springs: true, I suppose the volume of the springs is 0, just because in the contrary it is difficult to draw and second, I would need to take in account these volumes, and I don't want because I don't need these volume for my calculations.

Where are they? Their location matters

20 hours ago, xyrth said:

I don't see what you mean by "white inside" - inside of what?  Inside the container. I move out the parts of the white rectangles from the bottom, because the rectangles rotate around their axes (purple color) and I need to reduce their length. In the same time I move in the blue sphere (blue color).

 

Then you say the white stays outside of the container. You say the volume of the container is constant, but your diagrams show it changing on length, and the strips are polystyrene.: Yes, the volume of the container is constant, it passed from a parallelogram to a square, but even I move out the white parts of the rectangles, I move in the same volume of blue spheres.

If the volume of the container is constant, moving in a fluid means the white polystyrene must decrease in size. How does that happen? Unless you mean something else by "moving in"

Move out the white parts? You said they stay in the container. Is this a reference to their expansion in another direction, to remain constant volume?

 

20 hours ago, xyrth said:

Do you explain this in any detail? Yes, I can, just I don't know by what to start. I will try again.

 

It shows a sheet of white corrugated paper attached to a blue board being distorted from a parallelogram to a rectangle. Maybe. Meanwhile a blue and a white rectangle change shape. : I drew the side view of the device. At start, it is a parallelogram at final it is a square. If the depth of the container is 1m, then the volume of the container is always 1m³: I move out the white parts and I move in the blue spheres.

Again, what you mean by "move out" and "move in" is unclear.

 

20 hours ago, xyrth said:

Thanks to try to understand me.

I calculate the sum of energy of a deformation of a device. That device is composed of :

1/ A container with a constant volume, at start the volume is a parallelogram and at final it is a square

2/ White rectangles that rotate around their axes (purple color) when the container is deformed. I reduce the length of the white rectangle because at start the length is 1.414m and at final it is 1m. At start, there is near 100 % of the volume of the container fulled of the white rectangles inside the container, at final there is only 70.1% of the volume of the container fulled with white rectangles. I drew only 18 rectangles, but I can have in theory 10000. I could explain why after.

So the white does not remain constant volume. How much energy does it take to compress polystyrene? Can you recover that when it expands?

 

[xyrth]

1 hour ago, swansont said:

OK, so why not just say it's some fluid? 

Because I need to have the source of the attraction on the device. For that, I need to attract each sphere from the green line (bottom wall). I could take a real fluid but for what ? I don't need the force of gravity. With a real fluid there is friction, mass, and viscosity and the calculations are very complicated (compared to mine) to find the real sum of the energy.

 

1 hour ago, swansont said:

Where are they? Their location matters

Each sphere has a spring. Each spring is attached from a sphere and the green line. I could draw some springs but there are a lot. The orientation of the springs change during the deformation and follow the orientation of the lateral walls. But all the springs have the same orientation at a time. I drew the red line to symbolized the orientation of the springs.

 

1 hour ago, swansont said:

If the volume of the container is constant, moving in a fluid means the white polystyrene must decrease in size. How does that happen? Unless you mean something else by "moving in"

Move out the white parts? You said they stay in the container. Is this a reference to their expansion in another direction, to remain constant volume?

I move out the white parts of the polystyrene and I move in the same volume of blue spheres in the same time. The volume of container is constant at each time. Look at the animation, the white rectangles decrease their length and the white shape outside the container increases, it is the stock of the polystyrene. The blue shape outside the container, is a stockpile of blue spheres, that stockpile decreases when the device is deformed because I move in the blue spheres.

 

1 hour ago, swansont said:

Again, what you mean by "move out" and "move in" is unclear.

I thought the animation is ok. The container is deformed. The white rectangles rotate around the purple axes, so I need to reduce their length, I move out the container the the white parts from the "bottom", you can imagine the rectangles like assembly polystyrene, and I move out small parts more and more when the device is deformed. when the rectangles rotate, some space appears between the rectangles, I need to keep the pressure inside the container so I fill the space with blue shape.

 

I just understand, when I said the volume of the container is constant, it is not only the container itself BUT ALSO the volume inside the container: I need to have 100% of the container filled at each time, at start 100% of polystyrene, at final 70.7% of polystyrene and 29.3% of blue spheres. Because I want pressure always between walls, the walls of the container and the walls of the rectangles. Maybe that was not clear.

 

1 hour ago, swansont said:

So the white does not remain constant volume. How much energy does it take to compress polystyrene? Can you recover that when it expands?

I do not compress the polystyrene, I move out it perpendicularly to the screen. The polystyrene stays outside at final (look at the animation) but my stock of blue spheres is 0 at final because I move in all the spheres inside the container.

 

Edited May 16, 2018 by xyrth

[Strange]

59 minutes ago, xyrth said:

Each sphere has a spring. Each spring is attached from a sphere and the green line.

This is rather implausible. The springs have to pass through all the other springs and spheres to get to the ones furthest from the green line at the bottom. Why not assume all the spheres are attracted by gravity? (after all, the only purpose of the springs is to pull all the spheres down to the bottom with the same force)

59 minutes ago, xyrth said:

I move out the white parts of the polystyrene and I move in the same volume of blue spheres in the same time.

I still don't see where things are moving in and out of the container. And where do the extra blue spheres come from?

59 minutes ago, xyrth said:

Look at the animation, the white rectangles decrease their length and the white shape outside the container increases, it is the stock of the polystyrene.

How do you get blocks of polystyrene to change length?

59 minutes ago, xyrth said:

The blue shape outside the container, is a stockpile of blue spheres, that stockpile decreases when the device is deformed because I move in the blue spheres.

I thought the blue shape was the container?

Oh, OK. You mean that blue rectangle to the left. The springs cause these to jump from the container they are in to the other (deforming) container?

And, as you seem to be concerned with the energy in the springs, how far away is this other container?

59 minutes ago, xyrth said:

I thought the animation is ok.

I still find it pretty incomprehensible. But I am beginning to get a vague idea of what you mean.

But it all seems to rely on impossible behaviour of physical objects so I'm not sure how you expect to get realistic results.

59 minutes ago, xyrth said:

you can imagine the rectangles like assembly polystyrene, and I move out small parts more and more when the device is deformed. when the rectangles rotate, some space appears between the rectangles, I need to keep the pressure inside the container so I fill the space with blue shape.

How are you calculating the energy required to move these in and out of the container? 

 

Edited May 16, 2018 by Strange

[swansont]

1 hour ago, xyrth said:

I do not compress the polystyrene, I move out it perpendicularly to the screen. The polystyrene stays outside at final (look at the animation) but my stock of blue spheres is 0 at final because I move in all the spheres inside the container.

It becomes shorter. Its volume decreases. You have compressed it.

You say it stays outside, but that it's inside the container. That is not at all clear. How does the polystyrene get outside?

[Strange]

1 hour ago, xyrth said:

I do not compress the polystyrene, I move out it perpendicularly to the screen. The polystyrene stays outside at final (look at the animation) but my stock of blue spheres is 0 at final because I move in all the spheres inside the container.

How does replacing polystyrene with spheres (however you do it) affect the energy of the container?

And are you calculating the change in energy of the other containers you move the blue out of and the white into?

[xyrth]

4 minutes ago, Strange said:

Why not assume all the spheres are attracted by gravity?

Because with gravity I found the sum of the energy at 0, not here. My device is deformed like the source of gravity is on the device itself but if I put a planet on my device, the attraction will be concentric not parallel like I want: the orientation of the springs follow the orientation of the lateral walls.

 

5 minutes ago, Strange said:

This is rather implausible.

Think "in theory".

 

6 minutes ago, Strange said:

I still don't see where things are moving in and out of the container. And where do the extra blue spheres come from?

Have you look the animation ? I have a stockpile of blue spheres outside the container. At final the stockpile of blue spheres is empty and the stockpile of white parts is filled.

 

7 minutes ago, Strange said:

How do you get blocks of polystyrene to change length?

My device is unstable, I need an external device to control it but that external device count all the energies in/out. That external device do the job. (We are agree it is not really polystyrene, but ok if you want to call the white parts polystyrene.)

 

9 minutes ago, Strange said:

thought the blue shape was the container?

No. The container has 4 walls. I move out the white parts, I move in the blue spheres.

 

10 minutes ago, Strange said:

You mean that blue rectangle to the left.

You see rectangles, but blue spheres are like a fluid (with no mass and no friction).

 

11 minutes ago, Strange said:

How are you calculating the energy required to move these in and out of the container? 

I calculated the volume by the mean difference of pressure. The volume that moves in is the same the volume that moves out. I indicate in a drawing the mean pressures.

 

14 minutes ago, Strange said:

The springs cause these to jump from the container they are in to the other (deforming) container?

I didn't understand what you mean

 

14 minutes ago, Strange said:

And, as you seem to be concerned with the energy in the springs, how far away is this other container?

What other container ?

 

 

9 minutes ago, swansont said:

It becomes shorter. Its volume decreases. You have compressed it.

You say it stays outside, but that it's inside the container. That is not at all clear. How does the polystyrene get outside?

No I move out the white parts from the bottom, I don't compress it.

How the polystyrene get outside: an external device is necessary, that device count all the energies out/in. The sum must be at 0.

[Strange]

2 minutes ago, xyrth said:

What other container ?

The stockpile of blue spheres.

[xyrth]

5 minutes ago, Strange said:

How does replacing polystyrene with spheres (however you do it) affect the energy of the container?

That is the good question ! If I move out the white parts and move in the white parts, the sum of energy is well constant. Look at the case 1, in that case, the container is filled with blue spheres, from start, to end. At the angle 45° (arounf it), the laterals walls lost -0.207, the springs lost -0.207, the green line wins 0.414 (sure function of the angle of rotation). That is the problem (or a solution...) because when I move in the blue spheres, the springs help the green line 2 times than the springs lost in potential energy. The work of the lateral walls is already compensated by the energy to move out/in.

2 minutes ago, Strange said:

The stockpile of blue spheres.

The stockpile is not under pressure, there is only blue spheres inside it. I use a spring when I need it, and sure I count the potential energy of each spring.

[Strange]

6 minutes ago, xyrth said:

I calculated the volume by the mean difference of pressure. The volume that moves in is the same the volume that moves out.

If you are moving the same volume out and in, why bother moving anything? Why not just keep the same mix of spheres and polystyrene?

6 minutes ago, xyrth said:

I indicate in a drawing the mean pressures.

I don't see anything indicating pressure.

[xyrth]

13 minutes ago, Strange said:

And are you calculating the change in energy of the other containers you move the blue out of and the white into?

The stockpile is not under pressure. I use a spring when I need it.

 

For the pressure

I indicate "p=" in the drawing at start only, p=0, p=0.707, etc

Edited May 16, 2018 by xyrth

[Strange]

2 minutes ago, xyrth said:

That is the good question ! If I move out the white parts and move in the white parts, the sum of energy is well constant. Look at the case 1, in that case, the container is filled with blue spheres, from start, to end. At the angle 45° (arounf it), the laterals walls lost -0.207, the springs lost -0.207, the green line wins 0.414 (sure function of the angle of rotation). That is the problem (or a solution...) because when I move in the blue spheres, the springs help the green line 2 times than the springs lost in potential energy. The work of the lateral walls is already compensated by the energy to move out/in.

I don't know where those numbers come from.

Quote

The stockpile is not under pressure, there is only blue spheres inside it. I use a spring when I need it, and sure I count the potential energy of each spring.

Aren't the spheres attached to springs? So the further away the stockpile, the more energy in the springs.

10 minutes ago, xyrth said:

Because with gravity I found the sum of the energy at 0, not here.

That implies that you have got the energy associated with the springs wrong, then. If that is the difference.

Also, if all the spheres are being pulled to the bottom of the container by the springs, why is there any pressure on the other three walls of the container?

[xyrth]

3 minutes ago, Strange said:

Aren't the spheres attached to springs? So the further away the stockpile, the more energy in the springs.

Inside the container, each sphere has a spring between the sphere and the green line. Outside the container, I don't need the springs, they keep their length constant (they are fixed somewhere if it is necessary). I count the difference of potential energy from start to end (for a small angle or a big angle).

 

6 minutes ago, Strange said:

That implies that you have got the energy associated with the springs wrong, then. If that is the difference

I try to find the mistake in my calculations with that device.

 

7 minutes ago, Strange said:

Also, if all the spheres are being pulled to the bottom of the container by the springs, why is there any pressure on the other three walls of the container?

All walls have pressure inside the container. I calculated the work needed to rotate the lateral walls. The upper wall is fixed and the bottom wall (green) move perpendicularly to the force of pressure, so no work.

 

9 minutes ago, Strange said:

I don't know where those numbers come from.

I gave the integrals in the drawings.

[swansont]

18 minutes ago, xyrth said:

 

No I move out the white parts from the bottom, I don't compress it.

You still haven't explained what you mean by "move out the white parts" Do you remove them from the container?

18 minutes ago, xyrth said:

How the polystyrene get outside: an external device is necessary, that device count all the energies out/in. The sum must be at 0.

Yes it must, but you also have to be able to calculate the value. How are you doing that?

Quote

I calculated the volume by the mean difference of pressure.

How do you know what the pressure is?

[xyrth]

2 minutes ago, swansont said:

You still haven't explained what you mean by "move out the white parts" Do you remove them from the container?

Yes, like the animation shows it (the white stockpile increases)

 

2 minutes ago, swansont said:

Yes it must, but you also have to be able to calculate the value. How are you doing that?

The values of the energies ? It is easy, with the simplifications, I listed all the works:

a/ Rotate the lateral walls

b/ Move out/in

c/ Reduce the length of the springs

d/ Move the green line

I have the force of each spring, so I have the pressure. I gave the force of the spring relative to a volume because like that if I change the volume of the spheres all the calculations are correct. The only thing I didn't take in account it the coefficient of the sphere packing, if I take 0.74, I need to multiply all my calculations with that coef. it doesn't change the problem with the sum of energy and in theory I could fill all the volume with different diameters of the blue spheres.

7 minutes ago, swansont said:

How do you know what the pressure is?

I have the force of the springs, I have the pressure.

[Strange]

17 minutes ago, xyrth said:

All walls have pressure inside the container.

What is the source of this pressure? 

7 minutes ago, xyrth said:

I have the force of the springs, I have the pressure.

The springs only press (or pulls?) on the bottom of the container. Not the sides.

How do you calculate the pressure on the sides the container?

[xyrth]

1 minute ago, Strange said:

The springs only press (or pulls?) on the bottom of the container.

The springs pull.

 

1 minute ago, Strange said:

Not the sides.

Why not the sides ? The sides have pressure like the sides have pressure in a glass of water under gravity.

 

3 minutes ago, Strange said:

What is the source of this pressure? 

All the spheres are attracted in direction of the green line, so they pressure all they can, like molecules of water can do under gravity.

 

4 minutes ago, Strange said:

How do you calculate the pressure on the sides the container?

I have the force of the springs, so I have the pressure. I gave the force of the springs per volume like that I can change the diameter of the blue spheres.