An Interesting Spinning Top

It is common to think of a top spinning about a pointed tip or a rounded tip. Suppose there is a flat disk as the tip!

Like all spinning tops this is a gyroscope. It is very cleverly designed. The tip, in fact, is a dimple that creates a sharp circular edge at the middle of the blue hemisphere. The top will tend to spin about a contact point between this circular edge and the flat surface, which causes instability (as well as sideways displacement) such that the top then spins about points on the hemisphere. Instability continues until the top spins about a point on the great circle of the hemisphere. On the other side of this great circle the surface is conical and this provides a quick transition, or fall, so that the end of the spigot or handle makes contact with the flat surface. The top of the spigot, which is flat, becomes the tip about which the top spins. It would be interesting to simulate the mechanics of this. Someone gave this top to the author and it may have come from a Christmas cracker. Well done to whoever thought it up!

It seems the magnetic poles of the Earth have inverted a number of times. Electrons have two types of ‘spin’. Flywheels are of current interest in the context of energy storage and Formula One racing.

Video Demonstration

You can run the short video demonstration by clicking on the image above.

© Jim McGovern 2008