Gaussian Gun

[BillyJoe]

How does it work?

Perhaps he explains it, but I don't have sound.

At the start, there is a magnet in the centre with four bearings immediately to the left of it and a single one at the right end. This single bearing is pushed slowly towards the magnet. The end result is that the single bearing ends up where it started with the magnet and three of the original four bearings immediately to its left. The fourth bearing shoots off to the left at speed.
I can see that mometum it conserved, but why does it happen this way?

BillyJoe

 

[Donks]

Hmmm, I've seen that video before. I wonder where. Oh right! My signature

The guy doesn't actually explain it in the video. My guess is:
The ball is gently pushed towards the magnets, but the closer it gets, the more it's attracted, and it accelerates. By the time it hits the magnets it's going quite fast. The impact is transmitted to the other side almost perfectly, since the balls and magnets are pretty inflexible and thus don't dissipate much of the energy, so the last ball shoots off at roughly the same speed as the first ball hit.

 

[BillyJoe]

Hmmm, I've seen that video before. I wonder where. Oh right! My signature

Yep.

But why does the single bearing end up back where it started, with the magnet and the other three bearings immediately to its left? Why don't they stay where they make impact?

BJ

 

[Donks]

Yep.

But why does the single bearing end up back where it started, with the magnet and the other three bearings immediately to its left? Why don't they stay where they make impact?

BJ

Someone's going to have to do the math to answer your questions, and I really doubt it will be me...
Anyways, when the ball is approaching, and is attracted by the magnets, the magnets are also attracted. So the magnets and 4 balls move towards the incoming ball, and since they have more mass, they push the ball back a bit, ending up where it started.

 

[davidhorman]

I've seen something similar, but duplicated three or four times in a row. That's the way to get REAL velocity!

David

 

[Atlas]

I've seen something similar, but duplicated three or four times in a row. That's the way to get REAL velocity!

David

That's the version I remember. The magents held the balls about an inch apart. The contraption was even elevated so the balls rolled uphill. Each striking ball took the position of the ball it stuck. Each ball accumulated speed from being struck and from the magnet 1 inch further up the slope.

The last ball arced a nice cannonlike ballistic trajectory several feet long.

 

[BillyJoe]

I would like to see that.

 

[davidhorman]

The last ball arced a nice cannonlike ballistic trajectory several feet long.

Several feet? I'm pretty sure the one I saw (not live, a video on the web) could have taken someone's eye out, like this ->

It was arranged horizontally, with cubic magnets taped to a ruler, and only two balls on the forward side of each magnet, so it went from this:

o...Moo...Moo...Moo

to this:

...oMo...oMo...oMo ---------------------> o!

David

 

[TheBoyPaj]

This is my own, probably incorrect, take on it:

Split the event into two bits. When the first ball is attracted to the pack, it moves very fast and the pack moves slowly together. They strike. If the pack had been a solid mass it would have either stuck solid to the lone ball or would have bounced a couple of times. The end position would have been where the impact took place.

But it's not a solid pack, and the end ball is being held by a weaker force due to its distance from the magnets. So the huge force provided by a ball in direct contact with the magnet is more than enough to overcome the far balls' attraction and it flies off. The backwards movement of the pack is then just a matter of Newton's third law.

 

[Atlas]

David,

Now I believe we we both saw the same video. I cannot find it though. I've run across some other descriptions that place the magnet with the balls.

I was convinced from my poor memory that the maget was attached under the ruler. That is, the groove in the ruler let the balls roll forward but a magnet suspended a ball at 2 inch intervals. Each ball was then replaced by the rolling ball striking it.

I was researching maglev when I ran across the video. I think I mixed the two ideas. I sure wish I could find that video! The last ball shot out with incredible velocity for such a short acceleration distance.

Apparently a problem of the design is that, depending on the magnets chosen (the stronger the better for witnessing the effect) the impact of the bal bearings can shatter the magnet or reduce it's magnetic power.

Idea discussed here.

 

[Cecil]

Is this what you were thinking of?

 

[davidhorman]

That's the bunny.

David

 

[BillyJoe]

This is my own, probably incorrect, take on it:

Split the event into two bits. When the first ball is attracted to the pack, it moves very fast and the pack moves slowly together. They strike. If the pack had been a solid mass it would have either stuck solid to the lone ball or would have bounced a couple of times. The end position would have been where the impact took place.

But it's not a solid pack, and the end ball is being held by a weaker force due to its distance from the magnets. So the huge force provided by a ball in direct contact with the magnet is more than enough to overcome the far balls' attraction and it flies off. The backwards movement of the pack is then just a matter of Newton's third law.

This sounds right to me. It describes exactly what happens and I can't find fault with your explanations. It also explains why, in David's example, the magnets have to be fixed to the ruler. If the magnets weren't fixed, the result would be like this....

o...Moo...Moo...Moo

to this:

oMo...oMo...oMo ----------------> o! (magnets not fixed)

instead of this:

...oMo...oMo...oMo ---------------------> o! (magnets fixed)


I think,
BJ

 

[jmercer]

Could someone please explain something to me?

I understand why this works. I can see how it works. But I'm having a problem understanding how this doesn't violate any of the laws of physics. I know it doesn't, but how?

The ball pulled forward does so based on the magnetic pull. The ball propelled follows Newtons laws. Got all of this. Where I'm stumbling is where the ENERGY for this is coming from.

Yeah, I know, it's from the magnet. Sure, fine, got that.

But WHERE does the ongoing energy come from in the magnet? It can't be infinite; and AFAIK, it's not "generating" power - it's just a property of the magnet itself.

So... while I know it's impossible - it almost appears that force is being generated without an energy source - and I know for sure that perpetual motion machines are bogus.

So, what's the explanation? How are the laws of conservation upheld?

Thanks

 

[Dragon]

Could someone please explain something to me?

I understand why this works. I can see how it works. But I'm having a problem understanding how this doesn't violate any of the laws of physics. I know it doesn't, but how?

The ball pulled forward does so based on the magnetic pull. The ball propelled follows Newtons laws. Got all of this. Where I'm stumbling is where the ENERGY for this is coming from.

Yeah, I know, it's from the magnet. Sure, fine, got that.

But WHERE does the ongoing energy come from in the magnet? It can't be infinite; and AFAIK, it's not "generating" power - it's just a property of the magnet itself.

So... while I know it's impossible - it almost appears that force is being generated without an energy source - and I know for sure that perpetual motion machines are bogus.

So, what's the explanation? How are the laws of conservation upheld?

Thanks

The energy comes from setting up this system in the first place, placing all the ball bearings and magnets in their starting positions.

 

[Atlas]

But WHERE does the ongoing energy come from in the magnet? It can't be infinite; and AFAIK, it's not "generating" power - it's just a property of the magnet itself.

So... while I know it's impossible - it almost appears that force is being generated without an energy source - and I know for sure that perpetual motion machines are bogus.

So, what's the explanation?

Back in the 60s, in a high school class I liked to call North American Science, I learned it this way. Atoms are made up of charged particles and when they form into molocules and solids there is still a great deal of space between the particles. Metals have a structure with electrons in their outer shell that gives rise to strong bonds and enhanced energy conductance over other materials. Because of particle charge a tiny magnetic force is also inherent to the particles. That is, the total magnetic force is no greater in an iron magnet than in a regular piece of iron. The difference is that in nature's forge and man's, heat is applied to the materials and randomizes the orientations of the particles that make up the iron ore or the iron bar. Strong electrical charges can reorient the atoms of the iron bar, lining them up so that each particle's magnetic energy is oriented like it's neighbors. This orientation makes their magnetic charge additive. This implies that science can predict an upper limit to the achievable magnetic force from different materials. I think it has to do with the density of the solid and how good of a conductor of electricity it is - whatever the reason, it has to do with the inherent qualities of the material and it's atomic structure.

What I always found fascinating about this idea was that reorientation required a certain fluidity of the material. But the iron bar changes into a magnet and back showing no external physical changes at all. Perhaps it's analogous in some way to how heat affects the the atomic structure making the atoms or molocules vibrate faster and can sometimes even make the material glow in the visible spectrum without necessarily changing it's shape.

Heat however, and impacts to a magnet, have a detrimental effect on that magnet. They both cause a loss of force due to a randomizing influence the added energy has on the atomic structure of the magnet. I believe they literally vibrate the the atoms out of their alignment.

I seem to remember magnetism as an atomic alignment phenomonon but my memory has been shown faulty before. It may be limited to the electron's influence which seems to introduce a magnetic effect when current flows through a metal, but I think in a so called "permanent" magnet the magnetic
force arise from atomic alignments.

 

[jmercer]

The energy comes from setting up this system in the first place, placing all the ball bearings and magnets in their starting positions.

Maybe it's just counter-intuitive, but that doesn't seem right to me for some reason. That ball in the video has a pretty high velocity; maybe the initial work would match the amount of energy required, but subsequent "launches"?

Still feels like somethings missing... but thanks.

 

[Atlas]

Maybe it's just counter-intuitive, but that doesn't seem right to me for some reason. That ball in the video has a pretty high velocity; maybe the initial work would match the amount of energy required, but subsequent "launches"?

Still feels like somethings missing... but thanks.

I guess I missed the mark in answering what you weren't really asking. I'll try again.

The magnetic force is an inherent property of the magnet like gravity is an inherent property of the Earth. As long as the number of atoms remains constant in the magnet and as long as they remain aligned the force will remain constant.

I do think that each launch has a diminishing effect on the magnet (due to the impacts) but it's probably not that much. I think you need to think about the launch in terms of dropping a ball in a force field. Repeated launches in a gravity field don't surprise you. Magnetic fields are analogous for ball bearings.

I apologize if I again miss the thrust of your question.

 

[69dodge]

Maybe it's just counter-intuitive, but that doesn't seem right to me for some reason. That ball in the video has a pretty high velocity; maybe the initial work would match the amount of energy required, but subsequent "launches"?

Before each subsequent launch, you have to put the balls back where they started, which requires you to pull them away from the magnet they're stuck to, which means you're doing work. That's where the energy comes from. You.

 

[Atlas]

Before each subsequent launch, you have to put the balls back where they started, which requires you to pull them away from the magnet they're stuck to, which means you're doing work. That's where the energy comes from. You.

Yes! I think I'm caught up now. Resetting the balls is necessary for each new shot just as pulling the elastic bands back on your slingshot adds the the necessary potential energy to the system for each new shot. Like raising a ball 5 feet off the floor before dropping it. The human being is setting the system in a high potential energy state and the release triggers a change from potential to kinetic.