When a magnetic field moves through a conductor a current called an Eddy current is induced in the conductor due to the magnetic field’s movement. The flow of electrons in the conductor creates an opposing magnetic field to the magnet which results in damping of the magnet and causes heating inside of the conductor similar to heat buildup inside of power cords. The loss of energy used to heat up the conductor is equal to the loss of kinetic energy by the magnet.
And a note of caution if you decide to try this, these magnets are not for unsupervised children. In fact, everyone should be careful:
Neodymium magnets larger than a half inch are very strong and should be handled with extreme care since they can be dangerous. It is best to stick with neodymium magnets of quarter inch diameter or less.
From the Ri Channel's View the Tales from the Prep Room series, this is how you make a fluidized bed of sand: Making Sand Swim. Watch how these solids suddenly behave a lot like a fluid as air escapes between the sand particles, causing them to float. It’s definitely one of the more strange and fascinating demonstrations that we’ve seen.
The Floating Water Bridge, a demonstration by Dr. Elmar C. Fuchs. Two beakers are filled with triply deionized water. Electrodes are added to each, exposing the water to high d.c. voltage. A cylindrical water bridge forms between them that is stable enough to sustain itself across a few centimeters. Watch the water as the beakers are slowly separated. From FYeah Fluid Dynamics:
Gravity tends to make the water bridge sag and capillary action tries to thin the bridge, but both effects are countered by the polarization forces induced in the water by the electric field.