Why do we write units such as meters per second as $\mathrm{m\,s} ^{-1}$ instead of $\mathrm{m/s} $. Is the latter still a valid way of expressing units? Why are there two different ways of expressing the same unit of measurement?


It seems to come down to personal preference more than anything else.  The exponent notation could be argued to be slightly clearer in a purely linear setting like browser text, since it eliminates any potential ambiguity over whether you're using the forward slash as a division sign or a separator.($\mathrm{m\,s} ^{-1}$ is more useful as units get more complex as it removes any ambiguity around the 'division')

Both are still used because they are perfectly correct. According to the rule of indices (exponents), $\mathrm{m\,s} ^{-1}$ and $\mathrm{m/s} $ are the same mathematically.

  • $\begingroup$ Thank you @Loong. $\endgroup$ – Shishir Maharana Aug 10 '19 at 6:51
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    $\begingroup$ I have edited my answer. $\endgroup$ – Shishir Maharana Aug 10 '19 at 6:51
  • $\begingroup$ Minor comment (v3): sentences which begin with a mathematical abbreviation (here "m" for "meter," but also numerals like "3" for "three") are much more confusing for the reader than when such shorthand occurs mid- or end-sentence. Many style guides discourage numerals and abbreviations at the beginnings of sentences, and suggest either spelling out the relevant term or restructuring the sentence to put the abbreviation later. $\endgroup$ – rob Aug 10 '19 at 8:56
  • $\begingroup$ Thanks @rob, will watch out for such errors. $\endgroup$ – Shishir Maharana Aug 10 '19 at 9:06

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