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Grade upto college level Mechanics

When a stopper is pulled from a filled basin, the water drains out while circulating like a small whirlpool. The angular velocity of a fluid element about a vertical axis through the orifice appears to be greatest near the orifice. Explain.

Profile image of Shane Macguire
11 Years agoGrade upto college level
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1 Answer

Profile image of Deepak Patra
11 Years ago
The steady motion of the water is disturbed as the stopper is pulled from a filled basin. It gives the flow of the water irregular which breaks up into eddies and vortices. The result is that the water drains out circulating like a small whirlpool. As the fluid element circulates, the angular momentum remains constant. Thus, the angular velocity of the fluid element is inversely proportional to the radius of the whirlpool. At the orifice the radius of the circulating fluid element is small. So, the angular velocity about the vertical axis through the orifice appears to be greatest.