Rotating Saddle - tout est question de point de vue/d'origine

Un boule roule sur une pente ... sauf si vous lui rendez la pente "plate" ;)

Une expérience inutile mais pleine d'expérience si on arrive à imaginer qu'en tournant assez rapidement, l'arrête de la pente forme comme une mini surface ... plane qui va effacer la pente et que la balle fini par s'y loger comme une boule dans un bol =)
Et oui c'est limite côté réflexion scientifique mais c'est comme ça que j'ai réussi à l'expliquer à ma fille.

Rotating Saddle

La vidéo:

Crédits:

24 janv. 2013

A playground ball finds stability in a saddle when the saddle is rotating at the proper speed.

Mechanical analog of a "Paul Trap" particle confinement—a ball is trapped in a time-varying quadrupole gravitational potential. A large saddle shape (attached to a plywood disk) is mounted on a multi-purpose turntable. The saddle shape is essentially a quadrupole gravitational potential. Rotation of this potential subjects the ball to an alternating repulsive and attractive potential, much like the time-varying electric quadrupole potential of a Paul Trap used in trapping single ions or electrons.

The plastic ball used here is about 25 cm in diameter and was purchased at a toy store. The saddle consists of a rubber sheet and fiberglass, and was hand-made with help from Justin Georgi. The turntable is driven at about 110 rpm with a DC motor. We have observed this ball at this speed remaining stable for over 2 hours.

Slow motion footage recorded at 240 fps with a Casio EX-FH25. Thanks to Rob for letting us use the camera.

For more information on our demo and references for further study see http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pa...

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