# [NTG-context] writing physical quantities in maths mode

Morning all,
I have a need to write a lot of physical quantities - these should be
in text mode. Mostly I can manage, but subscripts are causing me grief

Eg
\startformula
\startmathalignment[n=3]
\NC \text{F}\NC =\NC {\text{GMm} \over \text r^2}\NR
\NC \text {force}_G \NC =\NC {\text{G} \times \text m_1 \times \text
m_2 \over \text r^2}\NR
\NC \text {force \low G} \NC =\NC {\text{G} \times \text m_1 \times
\text m_2 \over \text r^2}\NR
\stopmathalignment
\stopformula

In the second and third equantions I'd like force subscript G all in
roman, not italic, to follow the standard conventin.
The first one puts the G in the correct place, but in italic
The second one manages roman, but it's offset.
I suspect I could kludge this with hskips, but I think there should be
a more elegant solution.
If there is a paper on writing physics in ConTEXt (not maths... I have
found the helpful couple by Aditya Mahajan) that would save me time.

For most relationships I am planning to use predefine quantities, then
slot these in

\define \forceQA
{{\sl F}/\Newton}

\define \forceQU
{{\tf force}/{\tf newton}}

\define \forceQ
{{\tf force}}

(etc)

And this in the body

\startformula
{\forceQA \over \massQA} = \accelerationQA
\stopformula

\startformula
{\forceQU \over \massQU} = \accelerationQU
\stopformula

\startformula
{\forceQ \over \massQ} = \accelerationQ
\stopformula

Any more elegant solutions out there?

Thanks

Ian
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