Aluminum isn't normally magnetic, but as you carry a large aluminum tray toward the magnet, you find that the magnet repels the aluminum. Explain.
Once again, Lenz's law. The magnet induces a magnetic field in the moving aluminum tray to oppose its own, effectively pushing it away.
You eventually manage to get the aluminum tray up to the magnet. As long as the tray doesn't move, it experiences no magnetic forces. But when you drop it, it falls past the magnet remarkably slowly. What slows down its fall?
That trickster, Lenz. When the tray is stationary, the magnetic field of the magnet is not changing, but as soon as it moves, the field begins changing and an opposing field is induced.
Comments
I'm voting for this explaination:
Source: http://www.pureenergysystems.com/os/MagneticMotors/MXLO/theory/aluminum_and_mangets/index.html
*cringing at that url*
I loled pretty hard, actually.