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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
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Author
Topic: Falling Magnet (Read 13756 times)
