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The Physics Behind a YoYo

Nikki Nappi
Period E

As a yoyo master, I thought I should look into what makes a yoyo work. From what we learned about oscillation and what makes a yoyo come back to your hand so seamlessly (if you're skilled like me). When a yoyo is thrown down, the force of gravity acts on the yoyo's center of mass and pulls it downward. The rotation caused by the string wrapped around the axel is what makes the yoyo drop, which is a crucial part of what makes a yoyo fun. As the yoyo falls, its rate of rotation increases until it is at its maximum kinetic energy at the bottom, or when the string is full stretched out. The string is usually tied loosely around the axel so that it can continue to spin at the bottom.



However, the yoyo needs a little tug on the string to come back up. This tug increases the friction between the string and axel and causes the yoyo to begin rotating again and bringing it back to your hand. As the yoyo comes back to your hand, the kinetic energy of the yoyo is converted back into potential energy. This conservation of energy from the top to the bottom of the yoyo's path is what allows users to go at the "game" for hours. As long as the yoyo returns fully to the users hand, it will never slow down and the user can continue to cause the energy to convert back and forth.


The yoyo is not just a fun toy, but a great real life application of many physics concepts. This includes : rotation, energy (kinetic and gravitational potential), friction, and Newton's first law.

This video goes more in depth about the concepts behind a yoyo and why it works.

Now let's say you're not a yoyo master and decide to just swing it around in a vertical circle like a maniac. This can still be applicable to physics! In this video, Khan Academy shows an example of a centripetal force and gravitation problem involving a yoyo.



Sources :
How do yo-yos work? 
Yo-yo in a vertical circle example
Physics Behind a Yo-Yo

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