-A bicycle wheel
-2 handles for the axle
-Chain or rope suspended from large stand or ceiling
You can perform this experiment in a couple of different ways. Using the first method, you get the bike wheel spinning and then use the eyebolt in the end of the handle to hang the wheel on a hook which is connected to the end of a rope or chain. The second is to place the wheel on two circles of string hanging from the ceiling or a strong support. Spin the wheel and then cut one of the strings. In both instances the spinning wheel will remain upright. The wheel will also revolve around the remaining string or chain.
What's Going On?
Simply put, spinning objects are very stable and resist change in direction which is perpendicular to the rotation. By spinning the bike wheel, we're giving the bike wheel angular momentum. At this point, the wheel will resist change, but because of gravity it will begin to precess or rotate around the chain. The effect of gravity on a spinning wheel is a slow rotation around the string. This is called precession. The spinning wheel will rotate about an axis at right angles to the force axis.