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A comment on What Happens When You Drop A Magnet Inside A Copper Tube [video]. Parent comment

Re:What Happens When You Drop A Magnet Inside A Copper Tube ... by whatshisface on Monday February 03, 2014 @06:04PM (#7174189)
The inverse square law of force strength falloff would make it very hard to scale this linearly, that combined with the fact that weight increases with the cube of size means that the magnets involved would have to be incredibly strong.

Not impossibly strong mind you, if magnets can hold a hundred ton train car off the ground I am sure they could slow the fall of an elevator.

I'd not want to be inside that elevator with anything magnetic in my pocket, though.

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Re:What Happens When You Drop A Magnet Inside A Copper Tube ... by lutusp on Monday February 03, 2014 @07:25PM (#7174620)
> The inverse square law of force strength falloff ...

Because there aren't any magnetic monopoles, I believe in ordinary circumstances the relationship is inverse cube of distance. Reference: http://www.newton.dep.anl.gov/askasci/phy05/phy05629.htm

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Re:What Happens When You Drop A Magnet Inside A Copper Tube ... by IgorPartola on Monday February 03, 2014 @08:01PM (#7174758)
Yup, magnetic field falls off as 1/(distance3). That's why being 5 feet from an NMR magnet is bad news bears, while being 8 feet away is fine (numbers made up, do not test). I remember seeing signs all over the place at our labs at the uni, saying to not enter if you wear a pacemaker or if you are wearing a wrist watch.
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Re:What Happens When You Drop A Magnet Inside A Copper Tube ... by JackFr on Monday February 03, 2014 @11:49PM (#7175568)
Every elevator you've been in has been held up by a magnet. They're just not obvious inside the motor housing.
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Re:What Happens When You Drop A Magnet Inside A Copper Tube ... by throw_away on Tuesday February 04, 2014 @12:23AM (#7175674)
To be pedantic, they're usually held up by a counterweight or by hydraulics. They generally move by magnets, though.
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