Precious metals
November 4, 2009 – 2:03 pm{copper, silver}, {copper, gold}, {silver, gold} are fairly well known examples of binary alloys. Most jewelry is an alloy of these pairs, with a few other metals added in some proportion, intentional or not. Even when you buy the pure element, there is some fraction of impurities. A good and well studied system to admire and experiment with.
I was going to point you at a modeling site, with an uploaded molten gold in a box model file, but I just crashed my browser so I’d better go. The software is Molecular workbench, the company is Concord Consortium, and the website is www.concord.org/modeler. The code is a work in progress and has been known to be crashy occasionally. Very worth figuring out.
Lots of demos sweep me off my feet and then are put away before I think to write about them. One that we do tomorrow it to break a wooden beam, 1.2 cm x 1.5 cm by 145 cm, which is supported on each end by a raw egg. The eggs are set on end on tables separated by 140 cm, and are stood up in a small wad of plasticine. The beam rests on the eggs’ tops only, and spans the space between the tables. The performing scientist swings a metal rod down at the center of the beam, which done right breaks the beam quickly enough that the motion of the ends is upward. The broken pieces each rotate around their own centers of gravity, and the eggs go unbroken.
We shall see. There are three beams, and a dozen eggs. What could go wrong?
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