Stuff You Should Know SYSK's 12 Days of Christmas… Toys: How Yo-Yos Work
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Dec 12, 2025 Discover the fascinating physics of yo-yos, from the mechanics of inertia and angular momentum to how they 'sleep' and perform tricks. Delve into the rich history of this beloved toy, including its Filipino roots and the innovations of key figures like Pedro Flores and Donald Duncan. Learn how design changes, such as ball bearings, revolutionized yo-yo performance, and uncover quirky trivia, including their use in space tests! Top it off with fun anecdotes and surprising facts about yo-yos throughout history.
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Why Yo-Yos Can Sleep
- Modern yo-yos combine linear and angular momentum to enable tricks like sleeping and walking the dog.
- Angular momentum and gyroscopic stability let the yo-yo spin in place and resist axis changes while sleeping.
How Yo-Yos Became Big Business
- Pedro Flores popularized the modern Philippine yo-yo design in the U.S. and later sold the business to Donald Duncan.
- Duncan trademarked "yo-yo," but courts later ruled the term generic and the company eventually went bankrupt.
Mass Distribution Extends Spin Time
- Increasing mass farther from the axle raises a yo-yo's moment of inertia and prolongs sleep time.
- Design changes like wider outer rims exploit this to keep yo-yos spinning longer.
