Hi Doug,
Have a look at Bug 2160 http://bugs.webwork.maa.org/show_bug.cgi?id=2160
There was a problem with Newtons per Coulomb definition in the Units.pm file, so I fixed it and added in 46 more units, hopefully covering all your needs, but it hasn't made it into the production release. Let me know if it works for you.
cheers,
Boyd
WeBWorK Problems
more physics units
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