June 14, 2017

How Fidget Spinners Work: It’s All About the Physics

By Jeanna Bryner, Live Science Managing Editor
Credit: idan gamliel/Shutterstock – via livescience.com


Fidget spinners ― kids spin them and spin them ― and while parents may not “get” why the boomerang-shaped toys have caught on with such force, there’s real physics to explain how the distracting devices work.

“I was introduced to fidget spinners a few months ago by professor Kenneth Brecher from BU [Boston University],” said Paul Doherty, a physicist at the Exploratorium in San Francisco. “He makes his own spinning toys and handed me a fidget spinner and asked me to guess what it was. I described what it did but had no idea why someone would buy one ;-),” Doherty told Live Science in an email.
For Doherty, the spinners are interesting for another reason: “To me, these show the coolness of ball bearings that reduce friction and allow things to rotate freely for a long time.” (On a basic level, friction is the resistance to motion that occurs when one object moves relative to another.)
Here’s a look at what’s happening when your child, or you, balance a fidget spinner on your finger and give it a whirl.
Ball bearings are key to this spinning toy. To understand why, try this: Slide a block of wood or other material across the floor.
Then do the same with a marble. “I bet the marble goes farther,” Doherty said. That’s because friction associated with rolling motion is typically less than so-called sliding friction.
This same principle can be applied to the spinners. At the center, and on each of the three “wings” of the spinner, is a bearing race, which is a circular channel around which tiny balls roll with low friction, Doherty said.