[Jaaanosik (OP)]

Yes!

All right, good. Then here is the next question: do you agree that, before the ship's engine is turned on, the total linear and angular momentum of a stationary ship is also zero?

In regards to your question about the CD players: he did give them angular momentum. Pushing an object off-center results in a transfer of angular momentum.

In regards to your question about the cat, the total angular momentum is unchanged. The total angular momentum starts at zero and ends at zero. The cat did not generate any net angular momentum. If you actually paid attention to the very video you posted, you would realize that.

Kryptid,
I am paying attention to the video I posted. This is digging deeper.
It is very import, we have to settle this.
Cat started with zero angular momentum, generated half a turn and stopped the rotation, ended up with zero angular momentum again.

Where did the NET half turn come from?
Jano

[Jaaanosik (OP)]

...
In regards to your question about the CD players: he did give them angular momentum. Pushing an object off-center results in a transfer of angular momentum.
...

Kryptid,
what transfer you are talking about?
I thought you were saying a linear momentum is a linear momentum and it does not have an angular momentum.
I thought you were saying the linear momentum cannot be converted to angular momentum.
Jano

[Kryptid]

It would be nice if you would be respectful enough to stop skipping over my questions. This is a give and take. You can't expect me to keep answering your questions if you won't answer mine in return. If you answer this question:

Then here is the next question: do you agree that, before the ship's engine is turned on, the total linear and angular momentum of a stationary ship is also zero?

Then I will answer yours.

[Jaaanosik (OP)]

It would be nice if you would be respectful enough to stop skipping over my questions. This is a give and take. You can't expect me to keep answering your questions if you won't answer mine in return. If you answer this question:

Then here is the next question: do you agree that, before the ship's engine is turned on, the total linear and angular momentum of a stationary ship is also zero?

Then I will answer yours.

..
...
All right, good. Then here is the next question: do you agree that, before the ship's engine is turned on, the total linear and angular momentum of a stationary ship is also zero?
...

Yes, agreed,
Jano

[Kryptid]

Yes, agreed,

Okay then, thank you. Since we are in agreement that the ship starts out with zero linear momentum and zero angular momentum, we know that the total momentum of the system starts out at zero. If this is the case, then do you also agree that, in accordance with the conservation of momentum, the total momentum of the ship at the end of stroke one must also be zero?

Kryptid,
I am paying attention to the video I posted. This is digging deeper.
It is very import, we have to settle this.
Cat started with zero angular momentum, generated half a turn and stopped the rotation, ended up with zero angular momentum again.

Where did the NET half turn come from?
Jano

Net angular momentum is not required in order to perform a turn. The solution to the problem is explained at about minute four in the video you linked. For more information, Wikipedia has an article explaining it as well: https://en.wikipedia.org/wiki/Falling_cat_problem

Kryptid,
what transfer you are talking about?
I thought you were saying a linear momentum is a linear momentum and it does not have an angular momentum.
I thought you were saying the linear momentum cannot be converted to angular momentum.
Jano

They are separate quantities. I'm actually rather amazed that you didn't pick up the solution from the very video you linked earlier from Khan Academy. It explained that the ball hitting the paddle has angular momentum because it is hitting off of the axis' center. It stated that there would be no angular momentum if the ball hit exactly on the axis, despite the fact that the ball has identical linear momentum in both cases. It's exactly the same scenario with pushing the CD player. A force pushing off-center applies angular momentum.

[Jaaanosik (OP)]

Yes, agreed,

Okay then, thank you. Since we are in agreement that the ship starts out with zero linear momentum and zero angular momentum, we know that the total momentum of the system starts out at zero. If this is the case, then do you also agree that, in accordance with the conservation of momentum, the total momentum of the ship at the end of stroke one must also be zero?
...

No, because release of potential energy changes boundaries/dynamics of the system.
You hold a kilo in front of you in your hand - momentum zero, you let it go and the momentum is not zero.
A release of potential energy can change arrangement of inertial forces that can lead to conversion/transfer between linear and angular momentum.
Jano

[Jaaanosik (OP)]

...

Kryptid,
I am paying attention to the video I posted. This is digging deeper.
It is very import, we have to settle this.
Cat started with zero angular momentum, generated half a turn and stopped the rotation, ended up with zero angular momentum again.

Where did the NET half turn come from?
Jano

Net angular momentum is not required in order to perform a turn. The solution to the problem is explained at about minute four in the video you linked. For more information, Wikipedia has an article explaining it as well: https://en.wikipedia.org/wiki/Falling_cat_problem
...

Kryptid,
can cat turn around without releasing a potential energy?
Where is the change of 0 angular momentum to some angular momentum to 0 angular momentum coming from?
The same as the above, reconfiguration of the inertial forces. This costs energy.

potential energy - angular momentum
kinetic energy - linear momentum

[Jaaanosik (OP)]

...
They are separate quantities. I'm actually rather amazed that you didn't pick up the solution from the very video you linked earlier from Khan Academy. It explained that the ball hitting the paddle has angular momentum because it is hitting off of the axis' center. It stated that there would be no angular momentum if the ball hit exactly on the axis, despite the fact that the ball has identical linear momentum in both cases. It's exactly the same scenario with pushing the CD player. A force pushing off-center applies angular momentum.

Kryptid,
Yes, but the effect might be different.
See the CD players ON and OFF.

When the CD players are OFF then the center of mass moves away at constant velocity.
It has a constant linear momentum.
CD players have also constant angular momentum.

When the CD players are ON then the center of mass moves on a chaotic trajectory, forward, sideways, up, down, backwards, ...
The rotating CDs generate torque, all the torque force vectors are directed to an intersect - the potential well.
Pushing the CD players will cause the wobble.
A part of the original linear momentum/kinetic energy will be spent on climbing from the potential well so not all momentum/energy generates the forward and rotational motion,
Jano

[Jaaanosik (OP)]

...
They are separate quantities. I'm actually rather amazed that you didn't pick up the solution from the very video you linked earlier from Khan Academy. It explained that the ball hitting the paddle has angular momentum because it is hitting off of the axis' center. It stated that there would be no angular momentum if the ball hit exactly on the axis, despite the fact that the ball has identical linear momentum in both cases. It's exactly the same scenario with pushing the CD player. A force pushing off-center applies angular momentum.

Kryptid,
When the CD players are OFF.
Can we say the original linear momentum is split into the new linear momentum plus the new angular momentum?

lm_orig = lm_new + am_new

Jano

[Kryptid]

No, because release of potential energy changes boundaries/dynamics of the system.

No it doesn't. That would violate conservation of momentum. A closed system cannot experience a change in net momentum. Period. That's not debatable.

You hold a kilo in front of you in your hand - momentum zero, you let it go and the momentum is not zero.

The momentum is still zero because the Earth is pulled up towards the kilogram with just as much force as the kilogram is pulled down towards the Earth. The momentum of the Earth becomes equal and opposite to the momentum of the kilogram. So the total momentum is unchanged.

A release of potential energy can change arrangement of inertial forces that can lead to conversion/transfer between linear and angular momentum.

First of all, no, it can't. Noether's theorem makes it clear that linear momentum and angular momentum are their own separate conservation laws. Arguing against Noether's theorem is like arguing against the Pythagorean theorem.

Second of all, your ship starts off with neither linear nor angular momentum. So the ability to convert one into the other would not make the engine work either. You can't get any linear momentum from angular momentum because there isn't any angular momentum present to work with.

can cat turn around without releasing a potential energy?

The potential energy comes from the chemical energy in the cat's metabolism.

Where is the change of 0 angular momentum to some angular momentum to 0 angular momentum coming from?

It isn't. The angular momentum remains zero throughout the entire process of the cat turning.

potential energy - angular momentum
kinetic energy - linear momentum

Restating this nonsense will not make it true.

When the CD players are ON then the center of mass moves on a chaotic trajectory, forward, sideways, up, down, backwards, ...

If you knew what "center of mass" meant, you would know that isn't true. The center of mass will move along an identical trajectory whether the CD players are turned on or turned off. The reason for this is because the linear momentum received is identical in both scenarios.

A part of the original linear momentum/kinetic energy will be spent on climbing from the potential well so not all momentum/energy generates the forward and rotational motion,

That would violate conservation of momentum.

Can we say the original linear momentum is split into the new linear momentum plus the new angular momentum?

No, we can't. That would go against Noether's theorem. Linear momentum remains linear momentum and angular momentum remains angular momentum. No amount of arguing will change that.

[Jaaanosik (OP)]

No, because release of potential energy changes boundaries/dynamics of the system.

No it doesn't. That would violate conservation of momentum. A closed system cannot experience a change in net momentum. Period. That's not debatable.

You hold a kilo in front of you in your hand - momentum zero, you let it go and the momentum is not zero.

The momentum is still zero because the Earth is pulled up towards the kilogram with just as much force as the kilogram is pulled down towards the Earth. The momentum of the Earth becomes equal and opposite to the momentum of the kilogram. So the total momentum is unchanged.
...

Kryptid,
You and kilo in your hand. Are you a closed system with zero momentum?
You are saying no because the Earth got moved by the kilo.
We cannot stop, the Sun got moved by the Earth.
The galaxy got moved by the Sun.
The other galaxies got moved by our galaxy.
The Universe is unchanged only the internal conversions between its particles.

As mentioned before, all the particles in the Universe:
7am_1 + 3lm_1 + 5am_2 + 5lm_2 + ... + 2am_n + 8lm_n = 3am_1 + 7lm_1 + 5am_2 + 5lm_2 + ... + 8am_n + 2lm_n
Please, tell me where are you going to draw the boundaries of a closed system?
Jano 

[Kryptid]

Please, tell me where are you going to draw the boundaries of a closed system?

You can technically say that the entire visible Universe represents the closed system in question. But that is, of course, because gravity has an infinite range. Such is not the case if all you are doing is moving balls around inside of a spaceship. The ship itself represents the closed system then.

[Jaaanosik (OP)]

...
Second of all, your ship starts off with neither linear nor angular momentum. So the ability to convert one into the other would not make the engine work either. You can't get any linear momentum from angular momentum because there isn't any angular momentum present to work with.
...

Kryptid,
I do not follow what you are saying.
A loaded spring, potential energy, can start a rotation of a wheel, angular momentum.
Are you saying this cannot happen??
Jano

[Kryptid]

A loaded spring, potential energy, can start a rotation of a wheel, angular momentum

The recoil of the spring will send it in the opposite direction, creating an equal and opposite angular momentum to the wheel. The net angular momentum of the system remains zero.

Are you saying this cannot happen??

It can happen. The problem is that you are considering various parts of the system in isolation and not taking into account that momentum (angular or otherwise) is not a one-way street. Newton's third law will cause any donation of momentum to be counteracted by an equal amount of momentum in the opposite direction.

Just to make sure that you actually understand what conservation of momentum means (because it's far from clear that you do), take a look at this quote from "the Physics Classroom" website: https://www.physicsclassroom.com/class/momentum/Lesson-2/Momentum-Conservation-Principle

One of the most powerful laws in physics is the law of momentum conservation. The law of momentum conservation can be stated as follows.

For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision. That is, the momentum lost by object 1 is equal to the momentum gained by object 2.

The above statement tells us that the total momentum of a collection of objects (a system) is conserved - that is, the total amount of momentum is a constant or unchanging value.

I bolded the important bit. Based on this, do you understand that conservation of momentum means that the total momentum of a closed system cannot change?

[Jaaanosik (OP)]

...
It can happen. The problem is that you are considering various parts of the system in isolation and not taking into account that momentum (angular or otherwise) is not a one-way street. Newton's third law will cause any donation of momentum to be counteracted by an equal amount of momentum in the opposite direction.
...

What is causing the wobble of the CD players when they are ON and when they receive gentle external impulse?
Where is the action and counter-reaction coming from?
Jano

[Kryptid]

What is causing the wobble of the CD players when they are ON and when they receive gentle external impulse?
Where is the action and counter-reaction coming from?
Jano

And, once again, I will answer your question once you've answered mine...

[Jaaanosik (OP)]

What is a closed system?
From https://en.wikipedia.org/wiki/Closed_system

A closed system is a physical system that does not allow certain types of transfers (such as transfer of mass in or out of the system), though the transfer of energy is allowed.

The cat burning potential energy is losing atoms, mass is getting out of the system.
The rotating cat is not a closed system.
Jano

[Jaaanosik (OP)]

We should have done this long time ago.

Thus, in the absence of an external impulse, the linear momentum of a system remains unchanged.

The black ball is a closed system.
The dark blue wheel is a closed system.
The momentum is conserved till there is an external impulse.
The black ball hitting the wheel system is the 'external' impulse to the wheel system.
Yes, blue wheel and the black ball are subsystems of the bigger system.
Still this is the proper way to analyze the situation presented in the diagram.
The linear impulse from the black ball can act as an external angular impact of the blue wheel.

The conclusion is that the internal subsystems can change their values, conversion from one momentum to another.
Even a conversion from linear to angular.
I hope this settles the problem we were talking about for the last week or so,
Jano

[Kryptid]

What is a closed system?
From https://en.wikipedia.org/wiki/Closed_system

A closed system is a physical system that does not allow certain types of transfers (such as transfer of mass in or out of the system), though the transfer of energy is allowed.

The cat burning potential energy is losing atoms, mass is getting out of the system.
The rotating cat is not a closed system.
Jano

That didn't answer my question, now did it?

[Jaaanosik (OP)]

What is a closed system?
From https://en.wikipedia.org/wiki/Closed_system

A closed system is a physical system that does not allow certain types of transfers (such as transfer of mass in or out of the system), though the transfer of energy is allowed.

The cat burning potential energy is losing atoms, mass is getting out of the system.
The rotating cat is not a closed system.
Jano

That didn't answer my question, now did it?

I am not sure what is your question,
Jano