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[Phys-L] Buoyant cubes and magnets.



Diego Saravia pointed us to a video clip showing the dynamic effect of spinning an object on its intermediate axis of inertia.This looks quite strange in a zero-gravity field. I am reminded of two other effects: floating a cube on water and floating a magnet in air, both of which have a paradoxical aspect
A Quora user asked for the relative density of a unit cube which floats with a visible height of one tenth its unit length.One can suppose a cube might float with a face up, and edge up or a vertex up.It turns out that for a range of relative densities, the cube does NOT float face up, but rather with its top face at some lazy angle (e.g around 11 degrees) to the water surface
  http://geofhagopian.net/M1B/M1B-Spring10/HowThingsFloat.pdf

LevitationHere's the levitron - a magnetic spinner hovering over a magnet
https://www.youtube.com/watch?v=hri1IsxKw3E

or this one... .
https://www.youtube.com/watch?v=hu1jEWLZVug


Here's a still magnet hovering under a fast-spinning magnet
https://www.youtube.com/watch?v=zQ23j1hB-1o