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Rotational and inertial mechanics, overunity mechanism?


Seanie

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4 hours ago, swansont said:

The torque is internal to the system, exerted by the rod. Since it's internal, you can treat angular momentum as constant. You don't need to know the details of the torque the rod exerts, since it will exert an equal and opposite torque on the other mass. (similar to not needing to know the force of impact in a collision in order to apply conservation of linear momentum)

 

 

Sorry I don't understand. I don't see how any torque is exerted on either of the masses anyway or how the rod exerts torque. As I see it the rod is freely rotating, so nothing to exert a torque for or against it. Angular momentum is constant, yes I can see how that would be (i.e. since it is not gaining or losing speed). 

4 hours ago, studiot said:

Reach down give the rod a sharp twist with two fingers, like if you were spinning a coin on a table top.

After doing that I see the rod rotating. I may not be getting what you mean.

 

4 hours ago, studiot said:

The classic example is the ice skater, spinning on the ice.

Yes I am aware of that phenomenon but don't see how it applies to the mechanism. The rod does not get shorter (which would be like the ice skater pulling in her limbs).

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3 hours ago, Seanie said:

Sorry I don't understand. I don't see how any torque is exerted on either of the masses anyway or how the rod exerts torque.

What else is there?

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As I see it the rod is freely rotating, so nothing to exert a torque for or against it. 

No, you have constrained its motion to the x-axis.

 

If it were freely rotating then the system would simply rotate at some angular speed, end of story.

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This thread has gone very quiet lately. I would like to sum up what I'm aware of thus far re. this mechanism. The unbalanced rotation is made to rotate, this gives rise to the oscillating motion in the x-direction. Newtonian mechanics (NM) does not show any force arising to oppose the rod's rotation. NM provides a straightforward calculation showing that the mechanism produces energy indefinitely. This would be the end of the matter were it not for the belief that conservation of energy must apply somehow. No clear physics has been given here to show how that is. If someone were to propose this mechanism as overunity (I am not doing that, its not allowed here) I cannot show how they would be incorrect. This mechanism needs more investigation to try to solve the apparent mystery.

If I am missing something relevant to the main concept kindly share that here but only if you can show clearly and surely the correct physics to explain the mechanism. I hope this little investigation has been helpful and interesting for you, it has been for me. Thank you.

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9 minutes ago, Seanie said:

This thread has gone very quiet lately. I would like to sum up what I'm aware of thus far re. this mechanism. The unbalanced rotation is made to rotate, this gives rise to the oscillating motion in the x-direction. Newtonian mechanics (NM) does not show any force arising to oppose the rod's rotation. NM provides a straightforward calculation showing that the mechanism produces energy indefinitely. This would be the end of the matter were it not for the belief that conservation of energy must apply somehow. No clear physics has been given here to show how that is. If someone were to propose this mechanism as overunity (I am not doing that, its not allowed here) I cannot show how they would be incorrect. This mechanism needs more investigation to try to solve the apparent mystery.

If I am missing something relevant to the main concept kindly share that here but only if you can show clearly and surely the correct physics to explain the mechanism. I hope this little investigation has been helpful and interesting for you, it has been for me. Thank you.

Which one? The original one you claimed would continue to rotate, but would not, or the one with mass at m2 as well as m2 that would allow for rotation and oscillation at constant KE (assuming no friction or dissipative forces) with no extra energy to spare in doing so?

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4 minutes ago, J.C.MacSwell said:

with no extra energy to spare in doing so?

I'm referring to the mechanism in its up-to-date form, i.e. with m1 and m2 having mass >0. But isn't it clear that m2 will oscillate? If so then we have not explained where that energy comes from and if it comes from K.E. of m1's rotation we have not shown how that K.E. will be diminished.

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4 hours ago, Seanie said:

I'm referring to the mechanism in its up-to-date form, i.e. with m1 and m2 having mass >0. But isn't it clear that m2 will oscillate? If so then we have not explained where that energy comes from and if it comes from K.E. of m1's rotation we have not shown how that K.E. will be diminished.

They are connected by a rod.

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5 hours ago, Seanie said:

If I am missing something relevant to the main concept kindly share that here but only if you can show clearly and surely the correct physics to explain the mechanism.

 

Otherwise how could anyone be expected to see that the energy is provided by the K.E. of the rod?

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22 minutes ago, Seanie said:

Otherwise how could anyone be expected to see that the energy is provided by the K.E. of the rod?

Did I not mention at least a couple of times that an object with zero mass, such as the rod, has zero KE ?

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21 minutes ago, Seanie said:

Well ok but when I referred to the K.E. of the rod what I meant was the rod including m1 which is part of it.

You need to present a consistent model. m1 and m2 are the masses. The massless rod is separate.

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16 minutes ago, swansont said:

You need to present a consistent model. m1 and m2 are the masses. The massless rod is separate.

Sorry for the confusion. I thought we understood that m1 is a point mass at one end of the rod and m2 at the other end and that they all move as one since they are rigidly connected. This was the model all along so I don't see any inconsistency. So do you know the physics to explain this or what? 

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40 minutes ago, Seanie said:

Sorry for the confusion. I thought we understood that m1 is a point mass at one end of the rod and m2 at the other end and that they all move as one since they are rigidly connected. This was the model all along so I don't see any inconsistency.

Yes. m1, m2 and the rod - all distinct from one another 

40 minutes ago, Seanie said:

So do you know the physics to explain this or what? 

I’ve explained the boundary conditions. The system will conserve energy and the motion of one end is constrained. Momentum in the x direction will remain the same.  But you seem to be questioning this.

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7 hours ago, Seanie said:

I'm referring to the mechanism in its up-to-date form, i.e. with m1 and m2 having mass >0. But isn't it clear that m2 will oscillate? If so then we have not explained where that energy comes from and if it comes from K.E. of m1's rotation we have not shown how that K.E. will be diminished.

Is the rod still on/in a pivoting slider? 

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6 minutes ago, J.C.MacSwell said:

Is the rod still on/in a pivoting slider? 

Yes.

11 minutes ago, swansont said:

I’ve explained the boundary conditions.

No explanation here.

11 minutes ago, swansont said:

The system will conserve energy

no explanation here.

11 minutes ago, swansont said:

the motion of one end is constrained

How is that an explanation for what needs to be explained?

 

13 minutes ago, swansont said:

Momentum in the x direction will remain the same.

How does this even make sense let alone explain the concept? (e.g. momentum in the x-direction is obviously changing because of the constantly varying speed and direction).

 

16 minutes ago, swansont said:

But you seem to be questioning this.

Yes of course, who wouldn't? You seem to be avoiding the issue. You obviously don't understand the mechanics of the mechanism. That's ok, I have not met anyone yet who does.

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40 minutes ago, Seanie said:

 

 

How does this even make sense let alone explain the concept? (e.g. momentum in the x-direction is obviously changing because of the constantly varying speed and direction).

 

 

The motion of the centre of mass, of the m1/m2 system, cannot change in the x direction.

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1 hour ago, Seanie said:

Yes.

No explanation here.

no explanation here.

How is that an explanation for what needs to be explained?

If you want people to explain the underlying physics to you, you should clarify this. I was assuming you knew that already.

 

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How does this even make sense let alone explain the concept? (e.g. momentum in the x-direction is obviously changing because of the constantly varying speed and direction).

Is there a force in the x direction? Are you aware of the connection between force and momentum?

Seriously: if you don’t understand that you need to be tackling simpler problems first. I’ve been responding under the assumption that you wanted some pointers to solve the problem, not teach you physics or solve it for you.

 

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Yes of course, who wouldn't? You seem to be avoiding the issue. You obviously don't understand the mechanics of the mechanism. That's ok, I have not met anyone yet who does.

You can’t claim this while acting befuddled at first semester physics concepts

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