Not defined units

Without the worksheet it's impossible to be sure, but the most likely answer is that somewhere in the worksheet you defined m as a mass. That overrode the definition of m as 1 meter (there is no distinction between m as a variable and m as a unit). It also means the units for q cancel, because you have mass divided by mass. Unless you turned the warnings off (or you are using an old version of Mathcad) you should have got a warning when you redefined m. It will have a green zigzag line under it, and if you select the m it will say "This expression redefines a Mathcad built-in unit" Richard