# Quantity Equations

### Quantity equations relate the physical properties of measured
quantities.

Quantity equations are the explanations of physics that relate the
dimensions of Length, mass, time, temperature and substance. These
equations have been developed through a long history of scientific
study and discovery. The relationships described by quantity equations
result directly from basic physical "laws", such as Newtonian mechanics
the conservation of energy and momentum, the geometric definitions
of area, volume density etc.
Quantity equations do not specify that the input parameters have
specific units. Instead, quantity equations may be
solved using **any** *coherent system of units*.

What Calchemy does is coherse the various systems of units into
being mutually coherent! Calchemy allows you to enter the parameters
of *quantity equations* in whatever units you know them in,
and gives you the result in whatever units you want.

In practice, it has been common to employ equations that require the use
of convenient or familiar units of measure to represent the variables.
In contrast to Quantity Equations, these so called
"numeric" or
"engineering" equations contain some conversion factor that
represents the combined conversions required to make the units of
the equation coherent. These conversion factors are often
dimensionless, but in fact do have units (like ft/meter).
This (misleading) representation results in a *non-coherent*
equation.

### Calchemy cannot be used to solve non-coherent "numeric" or
"engineering" equations.

Calchemy Software Inc.

Fort Collins, CO

Last Updated 6/21/2009

© Copyright 1996-2009 Calchemy Software Inc.