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What makes a fidget spinner spin?

Fidget spinners, tri-spinners, jitter spinners: Whatever you call them, these addictive little toys actually contain some impressive feats of physics.

It turns out all the kids are wild about physics.

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It turns out all the kids are wild about physics.

WHAT MAKES A FIDGET SPINNER SPIN? 

The short answer is: balls.

The ball bearings inside the toy let the moving parts slide smoothly against one another. 

FLAT=FRICTION

Imagine trying to drive a car on skis instead of wheels, or pushing a book across a table. The friction churned up when you push a broad flat thing along another broad flat thing slows it all down.

ROUND=ROLLING 

Now, picture a layer of balls between the flat surfaces, so only a tiny part of a sphere rests on a surface, minimizing friction.  

THE PHYSICS INSIDE

The outside of the spinner spins for so long after a single shove thanks to angular momentum: The impulse a spinning object has to keep spinning.  

But it can’t spin forever. That’s a result, in part, of rolling resistance: Some of the energy from the first spin is lost over time, in the form of heat, slippage, and the surface of the ball and the surface of the case becoming slightly warped over time. 

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