# Unit issues in Mathematica 9

I posted the following on the Google+ group comp.soft-sys.math.mathematica and had no luck with responses. I've done a Google search and, to the best of my ability, used the documentation center.

The post I made was as follows:

I continue to receive "Unable to interpret unit specification m/s" (for example, but almost anything I attempt returns this message) with input: UnitConvert[55 mi/h,"m/s"] or UnitConvert[55 mi/h,m/s] or any other combination of quotes, omitted quotes, etc. Even the prediction/suggestion box, when I execute Quantity[55,"mi/hour"}, after it returns 55 mi/h, if I type in any combination of m/s, "m"/"s", "m/s", etc. into the box that opens when I select "Convert" in the prediction box yields the same "unable to interpret unit specification.

What am I missing? (As you may gather, I'm a Mathematica novice.)

-
Try UnitConvert[Quantity[55 , "Miles"/"Hours"], "Meters"/"Seconds"]. –  b.gatessucks Dec 18 '12 at 21:09
That's the sam as the answer I posted to MathGroup this morning. (Which raises a protocol/meta-question: should folks be posting the same question to both MathGroup and here?) –  murray Dec 18 '12 at 21:24
@murray ask it on Mathematica Meta. I believe it was discussed, but I cannot remember where. –  rcollyer Dec 18 '12 at 21:47
–  acl Dec 18 '12 at 22:24

It seems, if you are not going to use the "proper long name", you need to use Quantity Try
UnitConvert[Quantity[55, "mi/hour"], Quantity["m/s"]]

+1, exactly. You must use Quantity, otherwise it may not recognize what you are doing. –  rcollyer Dec 18 '12 at 21:20
@user5091, There's a "full" name for each unit, and then there are ways that you can type it that get properly recognized because WolframAlpha understands what you mean. If you do InputForm[Quantity["m"]] you'll see what I mean. That translantion only seems to be done inside Quantity. If you use the "full" name, you don't need the Quantity in UnitConvert –  Rojo Dec 19 '12 at 0:48
I agree however that it shouldn't be necessary to type Quantity. Perhaps it will be changed in the next upgrade. –  Rojo Dec 19 '12 at 0:50