BRAZILIAN NUT EFFECT
Among an assortment of things (whether they be nuts, sedimentary deposits, or other objects of varying sizes), larger pieces rise to the top over time in spite of their greater gravitas, while smaller objects tend to sink lower in the pile over time. Perhaps the small stuff is trickling through cracks. convection currents may also play a role, as might condensation of smaller particles. All of these possibilities and a few more probably contribute to the Brazil nut effect, but no one knows which ones, or to what extent, so no successful computer simulations of the phenomenon have been made.
Not only nut manufacturers, but also physicists, astronomers and geologists would all benefit from an understanding of the effect.
CHEERIOS EFFECT
You may or may not have pondered why your breakfast cereal tends to clump together or cling to the sides of a bowl of milk. Dubbed the cheerios effect by scientists, this clumping phenomenon applies to anything that floats, including fizzy soda bubbles and hair particles in water after a morning shave.
Dominic Vella, a graduate student now at Cambridge University, and Lakshminarayanan Mahadevan, a mathematician from Harvard University, were the first to explain the effect in terms of simple physics, which they did in a 2005 paper. The Cheerios Effect, they proved, results from the geometry of a liquid’s surface.
surface tension makes the milk’s surface cave in slightly in the middle of the bowl. Because water molecules in the milk are attracted to glass, the milk’s surface curves upward around the bowl’s edge. For this reason, pieces of the cereal near the edge float upward along this curve, appearing as if they’re clinging to the edge.
Also because of surface tension, cereal floating in the middle of your bowl dents the milk’s surface, creating a dip in it. When two pieces of cereal touch, their two dents become one, and, resting in it, they stick together.
STATIC
Static shocks are as mysterious as they are unpleasant. What we know is this: They occur when an excess of either positive or negative charge builds up on the surface of your body, discharging when you touch something and leaving you neutralized. Alternatively, they can occur when static electricity builds up on something else a doorknob, say which you then touch. In that case, you are the excess charge’s exit route.
But why all the buildup? It’s unclear. The common (and probably partly correct) explanation says that when two objects rub together, friction knocks the electrons of the atoms in one of the objects, and these then move onto the second, leaving the first object with an excess of positively charged atoms and giving the second an excess of negative electrons. Both objects (your hair and a wool hat, say) will then be statically charged. But why do electrons flow from one object to the other, instead of moving in both directions?
This has never been satisfactorily explained, and a recent study by Northwestern University researcher Bartosz Grzybowski found that it may not even be the case. As detailed in the June issue of the journal Science, Grzybowski found that patches of both excess positive and excess negative charge exist on statically charged objects. He also found that entire molecules seemed to migrate between objects as they are rubbed together.
PHYSICS SAGA 