Re: Pounds and Kilograms

*To*: mathgroup at smc.vnet.net*Subject*: [mg103660] Re: Pounds and Kilograms*From*: dr DanW <dmaxwarren at gmail.com>*Date*: Thu, 1 Oct 2009 06:41:42 -0400 (EDT)*References*: <h9v6po$99p$1@smc.vnet.net>

It is unfortunate that the usage messages and Doc Center files use the horribly muddled term "weight", as in "Pound is a unit of weight." In common English usage, "weight" is used interchangeably for "mass" and "force", because most common English people live near the surface of a single planet. It is not a term that belongs in a consistent, unambiguous scientific unit system. If all references to "weight" were replaced with "mass", than everything would be consistent in Mathematica. In the meantime, If you mean "the mass of an object that weighs a pound on the surface of the earth" than use Pound. If you mean "the force I exert to hold an object that weights a pound on the surface of the earth" than use PoundForce. I've explored the Units package a little further, and found that there are also a unit called PoundWeight (which is equal to PoundForce). I'm not sure if that clarifies the situation, or makes it worse. Easier just to dispose of the idea of weight altogether. Daniel