'However, if the object has protrusions so the ball bearing is not at the center of mass, you can start it spinning with a flick of your wrist,' he added. (The center of mass is the point at which you can balance an object, like the pivot point of a seesaw.) 'If you put the ball bearing at the center of a disk, you must start the spin by pushing on the outer part,' Doherty said, referring to the fact that the object's center of mass would be at the center. 'One flick of the fidget with a finger or a rapid twist of the wrist sets the fidget in motion, and it keeps going because of the low friction.'Īnd when it comes to spinning, shape matters. That's where a set of little hands comes into play: 'In a fidget spinner, you hold the center of one ball bearing, the outer bearing race spins around, and the outer parts of the fidget spin with the outer bearing race,' Doherty said. To get any object to rotate, you need to exert a twisting force, known as torque, on it. 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.
This same principle can be applied to the spinners.
