In short: The weight of an object falls off a rotating surface when a magnetic field is applied to the spinning object. If you’re in a car with a flat roof, your car levitates if you add enough weight to it to make it levitate; or, if you have a spinning dish of food in a glass jar, its weight can cause it to levitate if you attach enough weight to it. In the case of a bowling ball you don’t add enough weight to it to make it levitate; or if you add enough weight to a spinning toy to change its velocity a little bit, its body slowly slows down. An object with a flat bottom, such as a bottle of water, is unaffected by weight.
Another effect that can raise a spinning toy is its own inertia. A person running on a treadmill will exert a force on the treadmill when he or she walks. But the body will also accelerate as the motion of the object takes place, so the treadmill will appear stationary to the person’s eye. By applying a magnetic field to the spinning object, the body of the spinning toy will rotate in the opposite direction. As a result, the object will spin in a counter-clockwise direction, until finally, its body gets drawn back into equilibrium.
Another way in which an object loses momentum is if you add weight to it or move it to another location. When the object is spinning, the weight will have pulled it forward, and the object will slow down. This is why a bowling ball loses momentum when you bring down the bowling pins, or you can make something spinning in place spin slower. A spinning object, with its own momentum, will stop spinning.
Another way that the body rotates is if you increase its speed. In this case, the body will have no rotation and instead simply maintain its balance, which is due to the force of gravity (about 1 force per unit mass).
A little over a century ago, experiments in spinning toys were done by a German physicist named Albert Einstein, who suggested that gravity could raise an object from a position lying in a steady state of acceleration to a spinning state. The idea was not widely accepted until the 1920’s, since a spinning object would be heavier than it would be at rest.
This page was featured on Discovery.com in 2007.
In the 19th century, it was popularized by the author Aesop in “The Adventures of Huckleberry Finn.”
This article by David
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