Falling Magnet

[BEP]

I have asked this question in multiple forums. These forums range from the 'bag of idiots and freaks' to a couple you have never heard about and probably never will.

I believe I have the answer but this answer requires raising a root math hypothesis to proof level. I don't like the idea of giving Euclidean math any more foundation than it has. It may also require relating a rather disliked physics effect to magnetism. Nuff said about that happening  

The answer may not be as simple as you think.

Set yourself up for a very complicated experiment. This experiment requires a non-ferrous coffee can, partially filled with fine sand and a magnet (try a cylindrical or disk shaped one).

Identify each pole with a different color mark from the center of the pole to the outer diameter, in a straight line.

Hold the magnet about eye level and drop it in the can of sand.

Two things should happen that become apparent after a few 'magnet droppings' ( new term for this   )

What are they and why do you think they happen?

If you don't wish to bother with this experiment don't bother asking me about it.



   

[BEP]

No interest?

Somebody has interest. The question is always deleted on Yahoo or Answers.com. MIT says the falling magnet is no different than any other falling object. Berkely asked me to not post this or a related question again.

[Grumpy]

No interest?

Somebody has interest. The question is always deleted on Yahoo or Answers.com. MIT says the falling magnet is no different than any other falling object. Berkely asked me to not post this or a related question again.

I will try this test this weekend with a plastic Folgers coffee can and sand.

[BEP]

The sand is to prevent bounce or damage to the magnet. The container is not important as long as it provides enough area to hit and doesn't attract to the magnet.

[Grumpy]

so, you have to be able to "see" how the magnet lands in the sand.  OK

[Farrah Day]

The sand is to prevent bounce or damage to the magnet. The container is not important as long as it provides enough area to hit and doesn't attract to the magnet.

WW, can you just confirm one thing. You say the experiment requires a non-ferrous can, does it matter if the can is made from an electrically conducting material such as aluminium... or not? It just seems odd to be referring to a coffee 'can' as we tend to get our coffee in glass jars, but this may just be just down to semantics. Thanks.

[giantkiller]

How about I just hold a compass and turn around?

[BEP]

Glass jars?

Avoid metal of any type, if possible. You may drop the magnet on a pillow, if you wish. The point of the sand is to prevent damage to the magnet and leave the magnet in the same orientation it had during the fall.

I suggest you mark the poles so you can tell them apart.

Since there is no aluminum or copper tube in this experiment there will be no measurable drag due to eddy current.
Since the Earth's magnetic field is so weak nothing should happen from this.

Dropping a magnet a few feet 'should' provide absolutely nothing new.

Maybe it will do nothing interesting. If so, please send your latitude via PM.

[Grumpy]

 

[BEP]

Hmmm....

I had hoped someone would try this simple experiment.

My last attempt for a real answer resulted in a childish explanation of how a compass works. It was not even realted to the question 

One would think the same effect making airplane magnetic compasses useless during certain maneuvers would give the question credibility. 


All I want to know is: What Law of Physics dictates that a magnetic dipole must align itself perpendicular to the ambient magnetic field when it travels radially to that ambient field and why is the alignment always polarized the same way regardless of magnet shape?

The best answer I have received is: "Your question does not warrant our time".

The answer must be common and obvious. So, what is the answer?

Anyone?

[Grumpy]

(I'll have to sketch this out to see if this makes any sense and possibly delete or edit this later.)

The magnet is moving, and this must change something or add other variables to the system.   The fact that it is moving adds forces, for example.

[Microcontroller]

Since the Earth's magnetic field is so weak nothing should happen from this.

Dropping a magnet a few feet 'should' provide absolutely nothing new.

It depends on the shape of the magnet.
I got some Neodymium cubes that align with the earths field in a strong way.
THis is in horizontal rotation so i suppose if i drop it it will always land facing magnet north - earth north given enough distance to fall.

[BEP]

The shape of the magnet isn't much of a factor.

It is no factor at all over a fall of a few feet.

Air flow over the magnet seems to have no effect.

Until I hear a better explanation I am calling this 'Reverse Lorenz'.

[Grumpy]

When the magnet is falling, it is moving, the charges in motion produce a new current and associated forces in the magnet which alter the static forces.

I'll see what I can find to support this statement.

[Microcontroller]

The shape of the magnet isn't much of a factor.

I have done these experiments and that is why i respond to you question.
Now you answer back that my finding must be wrong.....

The shape of the magnet is of GREAT IMPORTANCE as it determines how good the magnet can align with the earths magnetic field.
Ever seen a compass with a bar shaped needle?

Thats all i'm gonna say.
I'm not intrested in arguing over test results because someone thinks he know better.

[BEP]

MC,

All I can tell you are the results of my experiments. If I had specially designed magnets I would probably prove you correct. I don't really care. The point is the magnet's polar axis aligns with the direction of travel, during a fall, 90 degrees away from where a motionless compass would point.

You may use a coin shaped magnet with the poles on the flat surfaces. The magnet will always land with a flat surface pointing down. Therefore, air resistance and concentration of magnetic field lines has very little, if anything to do with this. If you really had done the experiments, you would know this.

This has nothing to do with the simple function of a compass.

[Grumpy]

All I want to know is: What Law of Physics dictates that a magnetic dipole must align itself perpendicular to the ambient magnetic field when it travels radially to that ambient field and why is the alignment always polarized the same way regardless of magnet shape?

Is the north face up or down?

Have you tried it in the Southern Hemisphere?

[BEP]

I found a long time ago to let others find there own results on such a simple test, except when it is obvious they haven't performed it. In that case, I can at least tell who has performed the test. Not because I'm greedy or the results are that special but, because my results shouldn't have any effect upon other tests.

I have had some say their results in the Southern Hemisphere were flipped. No confirmation and I doubt that is true.

I haven't posted a video in a couple of years. Maybe it is time.

[Microcontroller]

MC,

All I can tell you are the results of my experiments. If I had specially designed magnets I would probably prove you correct. I don't really care. The point is the magnet's polar axis aligns with the direction of travel, during a fall, 90 degrees away from where a motionless compass would point.

You may use a coin shaped magnet with the poles on the flat surfaces. The magnet will always land with a flat surface pointing down. Therefore, air resistance and concentration of magnetic field lines has very little, if anything to do with this. If you really had done the experiments, you would know this.

This has nothing to do with the simple function of a compass.

If your results differ from mine we have a problem don't we ?

I was talking about the shape of the magnet and the horizontal rotation of it while the magnet is falling, and the position it will take when landed in the sand.

You say:

The shape of the magnet isn't much of a factor.

Which is not true, you can have shapes that react strongly to the earth's field and you can have shapes the react weakly to the earth's field.

You say:

Since the Earth's magnetic field is so weak nothing should happen from this.

Which is simply not true it's quite strong actually.

[Microcontroller]

If you really had done the experiments, you would know this.

This has nothing to do with the simple function of a compass.

These are some bad...bad words.
Your not worth my time.

[BEP]

If your results differ from mine we have a problem don't we ?

I was talking about the shape of the magnet and the horizontal rotation of it while the magnet is falling, and the position it will take when landed in the sand.

You say:

The shape of the magnet isn't much of a factor.

Which is not true, you can have shapes that react strongly to the earth's field and you can have shapes the react weakly to the earth's field.

The latter statement is true but the strength of the effect is to do with the size and density of the magnetic field, not the shape of the magnet.

You say:

Since the Earth's magnetic field is so weak nothing should happen from this.

Which is simply not true it's quite strong actually.

This was a statement made in advance of those thinking my tests were fake. Of course, the volume of the Earth's magnetic field means strength. That volume, indirectly, has a pronounced effect upon the results.

Never the less, my results indicate it isn't the reaction of the magnet's field to the Earth's magnetic field that matters.

A magnetic field is only a perception or view of something more fundamental. The only reason it is perceived is because the source is in relative motion to the viewer. When that relative motion ceases, so does the magnetic vector.

This is why a magnetic field can never be rotated about it's own axis.

Bad words?

You call me a liar and I posted the bad words?

Yes, our time discussing this has ended.

[MileHigh]

I'll share some thoughts on this issue, but I haven't done the tests.  Shoot me if you must.

The Earth's magnetic field relative to an observer on the ground is very weak, horizontal, and more or less in a North-South alignment.  It's also totally static.

WaveWatcher, you didn't make any comments about the orientation of the magnet when you drop it, if you unintentionally impart some spin or tumbling on the magnet when it leaves your fingers, the size and strength and shape of the magnet, etc.  You leave a lot of variables open there.  I realize you are probably implying that an average-sized magnet when dropped "normally" from eye-height will land every time like you stated, with it's magnetic axis perpendicular to the Earth's magnetic field and in an "up-down" or vertical orientation.

However, to be realistic, you would have to specify more information to make the test a bit more serious.

Nonetheless, let's look at what can we say about the test.   To keep things simple, let's neglect air friction.  Let's say it takes 1/3 of a second before the magnet hits the sand.  So, in other words, you have a magnet in free-fall, and it's "weightless" for 1/3 of a second.

The magnet has a certain mass and various moments of inertia.  The mass and the shape determine the moments of inertia.  There is a rotational energy upon release that depends on what kind of rotation or tumbling that might have been imparted on it when it leaves the experimenter's hand.  We also know that the magnet has a specific moment of inertia relative to the magnetic axis.  The strength of the magnet itself will affect how much torque the Earth's magnetic field imparts on it.

So you can distill the problem down to this:  You have a certain mass and shape of magnet that may be tumbling in the Earth's magnetic field.  How does it land in the sand after 1/3 second?

Since we are neglecting air friction, let's also ignore the possible tumbling for a second.  Now we are stripped down to the bare bones.  What would happen in this case, assuming that the magnet's magnetic axis is not lined up with the Earth's magnetic field?

The answer is pretty simple.  You have seen how a compass needle rocks back and forth.  That's what the falling magnet wants to do, oscillate back and forth in the Earth's static magnetic field.  A stronger magnet will make the oscillation frequency increase.  A larger moment of inertia will make the oscillation frequency decrease.  Then, you add the possible tumbling and then it gets complex because the tumbling is changing the torque on the magnet due to the Earth's magnetic field.

So when I factor in all of the things above, I can't explain why WaveWatcher always sees the magnet fall with the same orientation.  We know that the magnet wants to oscillate about the the axis of the horizontal magnetic field of the Earth.  If left for enough time the oscillation would decay and the magnet would end up lined up with the Earth's magnetic field, not at right angles to the field.  I can only guess that WaveWatcher is having some kind of coincidence happening when he does his tests.

MileHigh

[Microcontroller]

I can't explain why WaveWatcher always sees the magnet fall with the same orientation. 

Thats because he didn't do the experiment and i did.
I know it turns while it's falling.

[Grumpy]

Thats because he didn't do the experiment and i did.
I know it turns while it's falling.

Why does it turn while it's falling?

[muDped]

While the topic at hand is itself very interesting,
this discussion has developed a certain "strangeness"
which is reminiscent of other forums where
head games, high emotions and silliness abounds.

I was hopefully expecting evidence of greater maturity
from  the "experts."  I well understand we all have our
"moments" and our "territory" and our "honor" but,
really, isn't some of the commentary a bit juvenile?

Where is Spock when he's needed?