Run it up to speed and hold a neodymium magnet over the plate. You will feel both magnetic drag forces AND repulsion forces. Tie your neodyimum magnet to a string, a piece of tape, etc, and affix the other end of the string or tape to the plastic plate so the string stops the drag but not the repulsion. Watch out though, if the string lets loose, the EM drag will fling your brittle NIB magnet. A stack of NIB cylinders works great for doing this.
Teachers can strengthen their dead classroom bar magnets.
Do this to both ends and both sides of the bar, always starting from the center of the bar magnet and stroking towards the end, and always using the same pole of the NIB magnet stack. Bounce light from a distant small source off the water surface and onto a wall or screen. You will see a uniform oval projected spot of sunlight reflection from the water surface. In the projected oval of light, right at the location of the submerged magnet, you'll find a small bright splotch. The bright splotch is caused by a concave dimple in the water surface.