Possible proof that Gravity is a pull and not a push….

Maybe you have not read the post [ a few back] I made that said that this aspect would not prove push or pull as the effect is the same regardless?
I am now asking a different question regarding the scalloping effect I mentioned in the thread starter but no longer related to the issue of push or pull.

 

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I want to avoid posting a new thread on the issue just yet as there may be a simple explanation that I am unaware of that resolves what I consider as a paradox

 

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I did miss that retraction. However, I still do not see a scallop. I see a decrease in seperation in response to a decrease in resistive pressure, followed by an increased pressure at less spacing.

I think you are calling the fact that reducing pressure to allow movement to a closer position which result in higher pressure your paradox. Is that the case?

If so I see no paradox. The force hence pressure required to retain the spacing is specific. Reducing the pressure merely allows the movement. The movement alters the new equilibrium.

To me this issue is the equivelent of my "Black Berries are Red when they are Green".

 

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I'll repost the question:

 

sorry I over posted your post.

Yes I agree however say we have to move the magnet distance of 0.0001 mm. The pressure must be reduced to facilitate movement, this we can agree on but to stop 0.0001 mm closer the pressure would have to be increased more than the original pressure by a small amount to faciliate the new position.

If we take the logic to the very instant of movement we have the situation where pressure has to be reduced yet increased immediately after reduction.

If the pressure is not reduced there is no movement. If the pressure is not immediately increased the magnet will not stop it's movement.
So the pressure has to be reduced to a higher pressure as the magnet moves.

The act of increasing pressure as it is reduced is the so called paradox I am enquiring about.

For the magnet to close it's separation in a uniform and non-accelerating manner would require that the pressure be uniformly reduced and increased and I am suggesting that this is physically impossible to do thus scalloping exsts.

Again if we take the reasoning to the very instant of movement there exists this paradox of efforts I think.

 

we are moving the magnets by adjusting the pressure.....

 

If the situation is as I think it is, I would be very intigued as to how this would be handled mathematically.

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I understand the point you wish to make but I actually don't see a paradox. It is quite simular to the Triple Point of boiling water where you get ice, water and steam at the same temperature.

That is this fine point where you claim pressure must be both reduced and increased at the same instant is a point where the increase and decrease is equal in equilibrium.

That is they are the same amount. It is like the boiling and freezing of water at the same temperature.

Reducing the pressure allows the force to close the seperation until a new seperation and higher pressure are generated. This occurs because the force increased with the reduction of seperation.

If the force were linear then a reduction in pressure would allow movement until the original pressure was restored at less volume.

If you open a small bleed valve on your system pressure would steadily increase as the seperation decreased. That is you are merely setting the pressure below the equilibrium point against the force of closure.

 

Put a bleed valve on your system. As air is bleed off the rate of fall becomes a function of the differential pressure vs force. As the seperation decreases the pressure increases and the rate increases.

If the pressure is less than that required to maintain equilibrium then the force compresses. The only point where one could claim some paradox would be some finite but immeasureable pressure below equilibrium whihc allows the force to re-establish a new equilibrium at a decreased seperation which would be at a higher pressure.

I really don't have a problem with that. This is not unique to magnets or gravity. If you are holding a car from rolling down a hill which has an increasing slope, if you relax and the car moves then the car will require a higher braking force at the new slope.

So while you have drawn our attention to an amusing issue its physics are quite normal.

I don't see it that way. The higher pressure is at a different location and time. You are not both increasing and decreasing pressure at the same time. At equilibrium the +/- pressure is equal and no motion occurs. It only moves if you decrease and it then moves to re-establish pressure equilibrium at a higher pressure and different location.

 

I think I may have confused things by using pressure when I really mean effort. [ energy]

If I have two distances of separation that are 1 millimeter apart.

say at 100mm we need 50 units of effort to maintain that position.
To move to the 99mm position what do I have to do with the effort?

I am stuck on this notion that you would have to reduce the effort that is being used to maintain separation for the distance to close. Yet you would also have to increase the effort to maintain the 99mm position.
So the question remains:
How can you reduce the effort yet increase it after you reduce it and avoid a scalloping effect?

To move the magnet closer the effort must be reduced first, however to maintain the next position that is closer you have to increase the effort. So if this was graphed it would show a dip and then rize in effort being applied...yes?

 

MacM: And if CANGAS is around, your blackberries are colored "gone" when they are black.

 

I am just posting to second MacM's motion. I see the situation in exactly the same way he does. In addition to a lifetime of science study and theorizing, I have been a "hands on" person with much experience with mechanical systems. I understand this is true of MacM also.

Believe me, starting at A and bleeding OFF pressure is the only move you can make, except for some kind of violence, that will allow the magnets to execute their attraction for each other and draw nearer. If you have done this slowly and gently, you will be able to stop the bleed off gently

Hey! I just got what you are asking. If we slightly simplify and assume that the magnets are attracting in a simple inverse square fashion, then when they are at half their original distance, they will be attracting with 4x their original attraction. So, if originally 100PSI provided equillibrium, 4x attraction would require 400PSI for equillibrium?

Do I now correctly understand the basic points in your question?

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Think of it in terms of work and energy. You are moving it slowly so the pressure and the magnetic forces are always in equilibrium and there is never any appreciable kinetic energy. The force between the magnets increases monotonically as some function of the distance (r^2, r^5, whatever) and therefore the pressure must increase also. The magnetic force times the distance moved is the work done by the magnets on the gas and affects the pressure volume and temperature according to the ideal gas law. In order to continue reducing the volume that energy must go somewhere.

You can bleed off a little of the gas out of the cylinder. The volume of the gas you bleed off times the pressure in the cylinder is the work that the gas can do on something else such as you pneumatic power tools. So the energy goes from the magnet, to the cylinder, to the tools. If you stop bleeding air off into your tool at any point the magnet will stop since it is always in equilibrium. Each time you stop you will measure an increased pressure from the last time. But there is really no scalloping, energy is always going from magnet to cylinder to tool.

-Dale

 

And, if we want to get a lower pressure, we must add pressure. This is even worse than thinking about relativity.

The white knight's talking backward and the red queen's lost her head. Just hope I can keep MY head.

I must agree with this logic. But it ain't easy. :bugeye:

 

Scaloping. In the real world world here, when you first begin to let off pressure you cannot let off any ARBITRARILY small amount, which would enable the avoidance of even the smallest amount of scaloping. You must let off either no pressure or at least one air molecule. So, at the smallest microscopic level, you would have to endure some degree of stepping, or, quantum changing, of pressure.

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The motion of the magnets in this instance will never be a smooth motion. This is the origin of the conceptual "paradox". You cannot continuously move the magnets together at a constant speed in this way *(see below). There will always be a time gap between reducing the balancing force and allowing the magnet to move a small distance then increasing to a new and higher balancing force. The process of reducing and especially increasing a force does take time practically. However, assuming for the sake of explanation that all force changes happen instantly you will always require a certain amount of time for the magnet to move to a new position before stopping again (ie accelerating due to imbalanced force then suddenly decelerating due to a force that is even LARGER than the new higher balance force required --this may be another source of the query; if the force is dropped, allowing the magnet to accelerate, then balancing the larger force for the new closer distance will only make it continue at constant velocity, and therefore it will continue moving towards the other magnet and into an even closer range that has an even higher attraction force and require an even higher balance force as well as a higher deceleration force.) This is why it is difficult by hand to move two magnets together at a constant speed.
The time interval between starting to move closer and stopping can in theory be infinitely small but time is still required.(This explanation assumes that you are moving in single stages and stopping after each movement at a new closer position.)

It is actually possible, however, to allow the magnets to move together at a constant speed by having the same process as above for the start.(balance force is reduced) Then after one magnet has accelerated to a desired speed you maintain this velocity by creating a balance force that increases exponentially and always exactly matches the magnitude of the increasing attraction force. The resultant force on the magnet after initial acceleration is always zero and therefore the magnets can "drift" together at constant velocity. Although it would be very difficult practically to set a force that EXACTLY opposes the magnetic attraction force at increasing/decreasing distance. That's why when you try it by hand you can feel that it is extremely sensitive to your "natural error and inaccuracy" - they pull together unless you wedge your finger in between and gradually lower them together. I suppose this would be interesting maths but it might be simpler than you may have realised. (using the negative of the inverse square of the radius, so the inverse square of the radius would just be for the attraction force, the negotive of which is the balance force). Then again it would get more complex when you have the radius changing as a function of time, which is dependent on the chosen "drift" speed. And if you really want to make it interesting: instead of a constant speed of moving together...imagine a constant force and acceleration...

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I see I have generated a bit of confusion as the scenario, question etc has changed a few times as the thead has progressed however I think the "conceptual paradox" Trilobyte has mentioned is closest to what I think is happening.

I shall start another thread with a clearer purpose......

The thing is that if this concept is found to be valid then any attraction or repulsion that has the inverse function appled is essentially paradoxed. Which means that Gravitional attraction has a pardoxed function. I am not trying to de-paradox it but simply attempt to show it.
Hopefully the new thread will clarify in a way that you science guys can relate to.

 

This actually explains it quite well I think.

 

If you want a lower pressure you must add air. If you do it slowly then you need not increase the pressure, just the volume. However, since you are moving a volume against a pressure you are doing work on the magnets. Energy goes from outside to cylinder to magnet.

-Dale

 

I believe this is the correct view to make sense of it. One must assume a continuous work/energy change with no differential between the magnetic force and the resisting force. In such an integration there would be no "Scalloping" force as aadvocated by having a sudden differential aplied and a delayed return to equilibrium.