August 28, 2012

Nickle Mass Equals 5 Grams

Turns out that a nickle has a mass of exactly 5 grams. So you can use it to check that a scale is in calibration by placing the nickle on said scale and seeing if it reads 5 grams. Something about the government wanting 1 cent per gram, or something like that. Notice I used "mass" instead of "weight." All these years and that is still confusing. Mass is constant, weight depends on gravity, e.g., you are the same mass on the Earth and the Moon, but you are different weight on the Earth than you are on the Moon. Not sure about the new nickles, and you probably shouldn't use one this banged up. Some suggest even gluing 10 of them together to make a 50 gram calibration standard, though what about the weight of the glue? Every standard in the world is now related to the decay of some element, except for mass. That standard is still a 1 kg solid alloy of metals that are supposed to resist flaking and degradation because any time a piece of dust falls off, the standard changes. This is less than ideal. The original is in France, and the USA keeps a copy of the standard at NIST under a triple bell jar. It is only taken out once in a generation to make another copy or check the mass. Crazy and further reading:  http://physics.nist.gov/cuu/Units/kilogram.html
five cent nickle piece of money