[Jaaanosik]

When the CD players are ON then we need to consider the 'elasticity' of EM field of the motors.
One CD will be accelerated and the other will be decelerated when we apply the same external momentum as per the image.

Once the disks are spinning then the motors have no work to do (apart from overcoming bearing losses which, in principle could be practically zero).
So you can switch the motors off at that stage.
There's no EM field needed.
So there's no need to consider any elasticity it might have.

My post above shows what you missed.

No
It shows that you do not understand physics.

You say: "Once the disks are spinning then the motors have no work to do (apart from overcoming bearing losses which, in principle could be practically zero).
So you can switch the motors off at that stage.
There's no EM field needed."

That shows: "No
It shows that you do not understand physics."

It is you that does not understand the real world physics.
Escaping to unrealistic assumptions, really?

[Jaaanosik]

We apply the external forces as per the image, in the CDs parallel plane.

This is what I meant when I said: "The external momentum will distribute through the system differently and therefore the systems will move (translate/rotate) differently."

Why did you talk about that?
The question was about what happens after the disks are spinning.

There's a difference between the case of having the disks locked in place or not.
But since we are talking about CD players, and since I talked about being able topers play on the remote control, and get the disks spinning, it is clear that we are talking about the case where the discs can rotate.

Why are you talking about some nonsensical system where the discs won't play?

You started this two CD players taped together ON/OFF analysis.
When the CD players are OFF I split that scenario to two options because...
... the first time we discussed this I used term 'rigid' body and you mentioned the bearings in your post #357.
I made it an extreme, two scenarios for the simplicity, rigid body and friction-less bearings to point out the difference in the system.
So what are you talking about?

I am all for making the OFF scenario realistic as well. When bearings generate random friction each time we apply the external momentum.
Each time the system will respond differently.

[Bored chemist]

Escaping to unrealistic assumptions, really?

They are called simplifications- like the one where you have not mentioned air resistance.
Or is it only "escaping" when I do it?

[Bored chemist]

OK
So, let's try to agree a simple system that actually addresses the point.
There is no air resistance.
The bearings are frictionless and the motors are ideal so that, once they are up to speed the back emf exactly balances the applied voltage, no current flows and they draw no power. As a consequence, they produce no torque once the disks are spinning at 5 revs per second. The disks "coast" after that.

The two players are identical.
They are taped rigidly together feet to feet so that the angular momentum of the disks (and motors, for what it's worth) are identical in magnitude, but opposite in direction.
The cd players are (nearly) perfectly rigid (A perfectly rigid material would breach relativity).
We are doing the experiment in microgravity, so the effect of gravity from surrounding objects is small enough to ignore.
The players have remote controls which use IR or some such and which lets you start or stop them remotely without applying a significant force to them (we can ignore photon pressure from the IR).
The "stop" button on the remote actually drives the motor in reverse to apply a breaking force until the disk stops WRT the player and then switches off the drive power.
No other significant forces act on the players except those explicitly stated as part of the experiment.

Anything else we need to clarify?

[Kryptid]

It is you that does not understand the real world physics.

Said the guy who thinks conservation of angular momentum can be violated.

[Jaaanosik]

OK
So, let's try to agree a simple system that actually addresses the point.
There is no air resistance.
The bearings are frictionless and the motors are ideal so that, once they are up to speed the back emf exactly balances the applied voltage, no current flows and they draw no power. As a consequence, they produce no torque once the disks are spinning at 5 revs per second. The disks "coast" after that.

The two players are identical.
They are taped rigidly together feet to feet so that the angular momentum of the disks (and motors, for what it's worth) are identical in magnitude, but opposite in direction.
The cd players are (nearly) perfectly rigid (A perfectly rigid material would breach relativity).
We are doing the experiment in microgravity, so the effect of gravity from surrounding objects is small enough to ignore.
The players have remote controls which use IR or some such and which lets you start or stop them remotely without applying a significant force to them (we can ignore photon pressure from the IR).
The "stop" button on the remote actually drives the motor in reverse to apply a breaking force until the disk stops WRT the player and then switches off the drive power.
No other significant forces act on the players except those explicitly stated as part of the experiment.

Anything else we need to clarify?

OK, what's next?

[Jaaanosik]

It is you that does not understand the real world physics.

Said the guy who thinks conservation of angular momentum can be violated.

Not really, it is all about the space and time boundaries of the system discussed.
That's where the problems are.

Whatever BC comes up with in his ideal scenario I am going to ask what happens when the external momentum is going to applied during the time the motors are accelerating/decelerating the discs.
Are we going to claim EM fields are so perfect there are not going to be any 'skipped' steps?
That goes against randomness of the quantum physics.

[Kryptid]

Not really, it is all about the space and time boundaries of the system discussed.

I have seen you argue that linear momentum and angular momentum can be interconverted. That leads to violations of both conservation of linear momentum and angular momentum.

[Jaaanosik]

Not really, it is all about the space and time boundaries of the system discussed.

I have seen you argue that linear momentum and angular momentum can be interconverted. That leads to violations of both conservation of linear momentum and angular momentum.

They can, because they are system boundaries dependent.
Just check the video.
The beginning, CD player off and there is an external momentum.
The CD player rotates and the center of mass translates.
What momentum was applied? Angular or linear?

[Bored chemist]

OK, what's next?

OK, you presumably remember asking this

Do we have an agreement that the system demonstrates different attributes, the system behaves differently due to the internal motion of inner parts even thought the total net angular momentum is the same before the external impulse?

And saying this

First thing to recognize is the difference.
The 3 CD players at 0:49s when the CDs are not spinning inside.
There is an external impulse to the system of connected 3 CD players when they are not running.
The system starts to rotate/spin.
The system center of mass moves/translates at velocity v1.

The CDs are spinning inside at 0:55s.
There is an external impulse (it appears to be the same magnitude, but off center)  to the system of connected 3 CD players when the are running (CDs are spinning inside).
The system does not start to rotate. The system wobbles.
The system center of mass does not move/translates at velocity v1 (magnitude).
The system center of mass is resisting the straight line motion/translation.

Now, imagine wto pairs  (as discussed) of CD players.
One has the two disks  spinning and the other does not.
You apply a similar impulse to the two pairs
As you put it "There is an external impulse (it appears to be the same magnitude, but off center)"
But let's' be clear; in this case it is exactly similar, the same push in the same place on the shell of the CD player.

Do you believe that the motion of the two systems would be different.
 To sum up, the only difference is that the disks are (contra) rotating in one, but stationary in the other.

[Bored chemist]

What momentum was applied? Angular or linear?

Both unless the direction of the push happened to be directed exactly towards the centre of gravity of the object.
Was that meant to be a serious question?

[Kryptid]

They can

And thus you prove my original point.

[Jaaanosik]

OK, what's next?

OK, you presumably remember asking this

Do we have an agreement that the system demonstrates different attributes, the system behaves differently due to the internal motion of inner parts even thought the total net angular momentum is the same before the external impulse?

And saying this

First thing to recognize is the difference.
The 3 CD players at 0:49s when the CDs are not spinning inside.
There is an external impulse to the system of connected 3 CD players when they are not running.
The system starts to rotate/spin.
The system center of mass moves/translates at velocity v1.

The CDs are spinning inside at 0:55s.
There is an external impulse (it appears to be the same magnitude, but off center)  to the system of connected 3 CD players when the are running (CDs are spinning inside).
The system does not start to rotate. The system wobbles.
The system center of mass does not move/translates at velocity v1 (magnitude).
The system center of mass is resisting the straight line motion/translation.

Now, imagine wto pairs  (as discussed) of CD players.
One has the two disks  spinning and the other does not.
You apply a similar impulse to the two pairs
As you put it "There is an external impulse (it appears to be the same magnitude, but off center)"
But let's' be clear; in this case it is exactly similar, the same push in the same place on the shell of the CD player.

Do you believe that the motion of the two systems would be different.
 To sum up, the only difference is that the disks are (contra) rotating in one, but stationary in the other.

If the bearings are friction-less then CDs are not part of the system in this exact scenario.
There is no interaction between CD players and CDs when the external momentum is applied as I described.
This is what I mean, the boundaries are important.
So I agree with you that we would not see the difference under these ideal conditions in the example I described.
If we change time boundaries during the CDs acceleration then we need to specify ideal EM field (no skipping), again some unrealistic stuff.

[Kryptid]

If the bearings are friction-less then CDs are not part of the system in this exact scenario.

Seriously? Since when did friction define whether or not something was a part of a system or not?

[Jaaanosik]

They can

And thus you prove my original point.

Did the momentum of the CD player system changed when the external momentum was applied?
Where is the conservation? What boundaries are we talking about?

[Bored chemist]

If the bearings are friction-less then CDs are not part of the system in this exact scenario.

That may be true in the case where the impulse is exactly tangential to the rotation axis, but it is not true in general.

[Jaaanosik]

If the bearings are friction-less then CDs are not part of the system in this exact scenario.

That may be true in the case where the impulse is exactly tangential to the rotation axis, but it is not true in general.

Hence what I am trying to get across. The devil is in the detail.

[Kryptid]

Did the momentum of the CD player system changed when the external momentum was applied?
Where is the conservation? What boundaries are we talking about?

I don't know the specifics of this CD player system you are talking about, but conservation of angular momentum is proven by Noether's theorem. It isn't up for debate. If you think it isn't conserved, then you are the one who is mistaken.

[Jaaanosik]

If the bearings are friction-less then CDs are not part of the system in this exact scenario.

Seriously? Since when did friction define whether or not something was a part of a system or not?

Just think about this exact scenario and tell us how you can change the rotation of the CDs inside?

[Bored chemist]

If we change time boundaries during the CDs acceleration then we need to specify ideal EM field (no skipping), again some unrealistic stuff.

It may be a language thing,but that makes no sense.

No EM field is involved.
Time isn't good at obeying boundaries.
What do you mean?