Why does it work?
A fog machine is used to fill a drum made out of a bin. Hitting the drum forces air out of the hole, with the pressure differences within the air causing an air vortex. The pressure differences are caused due to air slowing down as it rubs on the side of the hole. Areas of 'slow air' tend to move towards areas of 'fast air'... better put; high pressure moves to low pressure. The mathematician Bernoulli found that moving air has less pressure than air that is still... this helps to create the fog ring as the slow air on the edge of the bin hole rushes toward the faster air in the center of the hole. The moving air has momentum and rolls the fog into a ring shape, also known as the vortex you see puffing out of the bin!
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