# What does $\mathrm{ms}^{-1}$ mean?

A baseball is hit with a velocity of $28.0 \ \mathrm{ms}^{-1}$. Should I just ignore this, or is it actually part of the question, what does it mean?

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$1 m \; s^{-1} = 1\; m/s$ is one meter per second. That's the same thing as 3.6 km/h and again the same thing as roughly 2.24 mph –  t.b. Aug 28 '11 at 13:03
Shouldn't this be migrated to the physics SE? –  Ｊ. Ｍ. Aug 28 '11 at 16:28
–  Willie Wong Aug 29 '11 at 13:00

It means meters per second (recall that $s^{-1}=1/s$, so $m \;s^{-1}=m/s$).

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And, strictly speaking, units should be in roman type 28.0 $\mathrm{m s}^{-1}$ not italic 28.0 $m s^{-1}$ –  GEdgar Aug 28 '11 at 13:27
I would also suggest a space between the units, as in $28.0\;\mathrm{m\;s}^{-1}$, lest it be misinterpreted as "$28.0$ per millisecond". –  Ilmari Karonen Aug 28 '11 at 17:41
Or even $28.0\ \text{m} \cdot \text{s}^{-1}$. –  Tanner Swett Aug 28 '11 at 22:06