Bladeless wind turbine inspired by Tesla

(PhysOrg.com) -- A bladeless wind turbine whose only rotating component is a turbine/driveshaft could generate power at a cost comparable to coal-fired power plants, according to its developers at Solar Aero. The New Hampshire-based ...

Chasing the black holes of the ocean

According to researchers from ETH Zurich and the University of Miami, some of the largest ocean eddies on Earth are mathematically equivalent to the mysterious black holes of space. These eddies are so tightly shielded by ...

Human eggs prefer some men's sperm over others, research shows

Human eggs use chemical signals to attract sperm. New research from Stockholm University and Manchester University NHS Foundation Trust shows that eggs use these chemical signals to choose sperm. Different women's eggs attract ...

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Fluid

In physics, a fluid is a substance that continually deforms (flows) under an applied shear stress, no matter how small. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids.

In common usage, "fluid" is often used as a synonym for "liquid", with no implication that gas could also be present. For example, "brake fluid" is hydraulic oil and will not perform its required function if there is gas in it. This colloquial usage of the term is also common in medicine and in nutrition ("take plenty of fluids").

Liquids form a free surface (that is, a surface not created by the container) while gases do not. The distinction between solids and fluid is not entirely obvious. The distinction is made by evaluating the viscosity of the substance. Silly Putty can be considered to behave like a solid or a fluid, depending on the time period over which it is observed. It is best described as a viscoelastic fluid. There are many examples of substances proving difficult to classify. A particularly interesting one is pitch, as demonstrated in the pitch drop experiment currently running at the University of Queensland.

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