Seanie

Yes. No explanation here. no explanation here. How is that an explanation for what needs to be explained? 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). 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.

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?

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.

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

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.

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.

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

yes it seems so to me anyway. Ok but how does that happen here? But to my understanding if a rotation (or anything else) changes speed its because some torque (or force) acted against its motion. Otherwise it would seem like a magical happening with no identifiable mechanics to explain it. By all means show me what I'm missing here. If you mean that the rotation may not continue for very long is that because of something about the couple itself? (if so I would love to understand that better), or is it because of friction or what?

If the rod's angular speed changes (i.e. it must slow down) to supply energy to the oscillation then there must be a torque opposing its rotation because from Newton's 1st law it will otherwise continue at the same speed. Or to put it another way, if it slows there must be a force (i.e. torque) or some resistance to its rotation, to slow it. Is that correct? To provide power to the oscillation it seems that m1's rotational energy is the only possible source of that power, yet how does this happen, I mean what are the mechanics of it exactly? Because I don't see a way for there to be such an opposing torque, do you?

Yes, that makes sense too and it is something I had overlooked, thank you. Now I'm wondering what would happen if m2 had a real mass. I suppose m1 would rotate then as well as m2 oscillating. If so then we are back to the old question of where is the torque coming from that would oppose the rod's rotation? If there is none then how to account for the energy to oscillate m2? Yes thanks for the example, I get the idea now. Sorry I thought the answer was contained in what I said here:

Ok, I get what you mean and that makes sense. The only thing is that I don't see how it relates to our mechanism here. To clarify my statement further: so if m1 is the rotating mass, rotating about the point m2 then m2 is the centre of the rotation, that's the "centre being free to move" that I referred to, it is free to move in a straight line in the x-direction. So when m1 is rotating (i.e. an unbalanced rotation) it will tend to pull m2, of course. How is that not the case? With your ball on a string its the same thing, your hand is at the m2 position (centre of rotation) and it will feel a pull towards the ball. Then since m2 if free to move in a straight line it will indeed move, how can it not? If you are saying it will not move that's what I don't understand. Thanks.

I'm not sure what you mean here, it certainly seems a bit derogatory, don't you think? You seem to not like the idea of the rod only being given an initial turning impulse (i.e. without translational force). Why is that? To keep the mechanism as simple as possible so as to focus on explaining what seems to be energy that is unaccounted for (an important matter surely), that's why I specified that the initial impulse only has a rotational effect on the rod about m2. Otherwise we would have to try to calculate the effect of translational force from the initial impulse which would unnecessarily complicate things. I suppose if the initial impulse was a moment that there would also be a translational force and if it were a couple there would not be. Are you clear now about the initial impulse or is there still something other than rotation of the rod that I need to consider (i.e. resulting from the initial impulse)? I'm not sure I get what you mean. We have a rotating mass because it has been given an initial impulse. Then because of its centre being free to move in a straight line the rotating mass will surely pull on its centre, will it not?

because m2 can move even though its KE =0. Also if m2 is moving that means that m1 must have an extra x-direction motion and that requires energy.

We can remove that all we like but we are then stuck with a mechanism that doesn't make sense. I agree. I had been working on similar mechanisms and for some reason had those labels and they just got carried over to this one. Then with all my notes being as they were I didn't want to come up with new names.

That means m2 doesn't have any motion. In that case do you not find it hard to imagine how a rotating eccentric weight would not pull on the centre of its rotation? If it does pull on it and the centre can freely move then why would it not move? I'm hoping that we are at least seeing major problems with our analyses (including mine).