A

David

Darling

paraboloid

The surface of a rotating liquid is a paraboloid

The surface of a rotating liquid is a paraboloid.


A paraboloid is the surface of revolution of the parabola. It is a quadratic surface described by the equation z = a(x2 + y2).

 

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A uniformly rotating liquid acquires a paraboloidal surface from the interaction of gravity and centrifugal forces, as can be seen by spinning a pan of liquid on a turntable. This surface is perfect for radio- and optical-telescope mirrors; a mirror surface can be made by spinning plastic resin in a dish while it sets and coating it with a metal.