The yo-yo is a toy
consisting of two equally sized disks of plastic, wood or metal,
connected by an axle with a string tied around it.
First becoming popular in the 1920s, “yo-yoing” is still enjoyed by both children and adults to this day. On the surface, the yo-yo is an incredibly simple toy. It's really nothing but a spool attached to a length of string.
But in the right hands, it can be something extraordinary! An accomplished yo-yoist can send the yo-yo flying out in all directions, make it hover in mid air, then snap it back into his or her palm.
Ordinary string and wood (or plastic) are brought to life!
The yo-yo is one of the most popular and enduring toys of all time. The ancient Greeks were playing with them more than 2,500 years ago, and there's some evidence that the Chinese had developed similar toys before that. In any case, the yo-yo has demonstrated that it's older than any other toy, except the doll.
When the yo-yo reaches the end of its string, the motion of the spinning discs tends to level the races out, so they are aligned with one another. With this, the ball bearings can move smoothly between the two races.
To wake the yo-yo, you jerk on the string. This tilts the outer race in relation to the inner race, increasing the friction on the bearings. The spinning motion of the outer race carries the yo-yo back up the string.
This mechanism makes it easier to keep a yo-yo sleeping, but it doesn't help much with waking the yo-yo up.
International Yo-Yo Open is the largest yo-yo contest in the world. It
is held every year in August at South Street Seaport in New York City.
In the inaugural 2007 contest, there were over 8,500 people in
attendance and the event received almost 30 million media impressions.
More information about this event can be found at YoYoOpen.com.
The World Yo-Yo is held every year in Florida, USA during early August or late July. This contest takes the winners from national yo-yo contests around the world and pits them against each other. Japanese players in particular have risen to the top of the yo-yo world.
A yo-yo competition normally consists of two parts, a set of compulsory tricks and a freestyle, where points are scored for each and the winner is the yo-yoer who scores the most points.
(References: Wikipedia, the free encyclopedia)