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Toy tops



The spinning top, a toy found across many of the world's cultures is a great example of a few key physics principles. The first is the conservation of angular momentum: with no outside forces present, something spinning must keep spinning. Because a top balances upon a tiny point, the is a nearly negligible amount of friction, and it continues spinning for a long time, demonstrating the law. But as friction slows the top, it becomes unstable and starts to wobble, leading to another principle called "precession." When the top wobbles, its axis of rotation tips sideways, making an angle with the table. This angle allows the force of gravity to exert a "torque" on the top, putting additional spin on it, and this causes it to swing (or precess) outward in an arc, still spinning as it does so. In an effort to conserve its total angular momentum, the top precesses faster the slower it spins; this explains why tops typically lurch outward just as friction brings their spinning to a stop.


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