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Brazil nut effect
Additional recommended knowledge
The Brazil nut effect is the name given to a phenomenon in which the largest particles end up on the surface when a granular material containing a mixture of objects of different sizes is shaken.
In a typical container of mixed nuts, the largest will be Brazil nuts.
The phenomenon is also known as the muesli effect since it is seen in packets of breakfast cereal containing particles of different sizes but similar density, such as muesli mix.
It may be counter-intuitive to find that the largest and (presumably) heaviest particles rise to the top, but there are several possible explanations:
The effect is of serious interest for some manufacturing operations; once a heterogeneous mixture of granular materials has been produced, it is usually undesirable for the different particle types to segregate. Several factors determine the severity of the Brazil nut effect, including the sizes and densities of the particles, the pressure of any gas between the particles, and the shape of the container. A rectangular box (such as a box of breakfast cereal) or cylinder (such as a can of nuts) works well, while a cone-shaped container results in what is known as the reverse Brazil nut effect.
The effect may also be of interest to geophysicists or geologists when studying the effect of vibrations on sand or other loosely contacting materials.
In astronomy, it is also seen in some low density, or rubble pile asteroids, for example the asteroid 25143 Itokawa.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Brazil_nut_effect". A list of authors is available in Wikipedia.|