How Yo-Yo's Work

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  • Topic: Moment of inertia, Kinetic energy, Angular momentum
  • Pages : 4 (1499 words )
  • Download(s) : 1902
  • Published : October 11, 2007
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The yo-yo is one of the oldest toys in existence. Despite its lasting popularity, it is one of the simplest toys around. The early versions of they toy were made simply from carved wood and a string. No one is quite sure of the origin of the yo-yo but many say China. Others say that ancient Greeks as far back as 2,500 years used yo-yos for entertainment. The motion and the process of playing with a yo-yo incorporates many concepts in physics of momentum, energy, friction, etc. With simply a spool and a bit of string a yo-yo is a fantastic model of physics hard at work.

In the first versions of the yo-yo, the string was tied directly to the spool, which made the yo-yo snap back up as soon as it was fully extended. In more modern versions of the yo-yo, the string is made into a loop around the spool, which allows for the yo-yo to "sleep" or keep spinning while fully extended. While the yo-yo is still in the user's hand, it has potential energy. It has the potential to fall, and also the potential to spin. Once the yo-yo is released, it falls towards the ground and converts its potential energy into kinetic energy. As the yo-yo falls, it builds up linear momentum and at the same time it builds up angular momentum as the string unwinds and the yo-yo spins. This builds up the yo-yo's rotational velocity so that when it sleeps, it can spin very quickly so that it can sleep for lengthy periods of time. When the yo-yo's string is completely extended, the built up angular momentum combined with extremely little friction keeps the yo-yo spinning (in the case of the modern yo-yo that can sleep). This spinning of the yo-yo produces gyroscopic stability and the yo-yo's axis stays perpendicular to the string so long as the yo-yo is still spinning fast. When the yo-yo is sleeping, it is rotating away from the user. This means that the angular acceleration points toward the left based on the right hand rule. The concept of precession is also very important in yo-yos. If the...
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