A physics teacher saw the following in a student's work:

$f=\mu n$



The teacher realized the student's capitalization was correct. What are these equations used for?

  • 3
    $\begingroup$ Did you just turn this comment into a puzzle? :) $\endgroup$
    – Riley
    Aug 4 '18 at 17:33
  • 3
    $\begingroup$ To show the importance of Bass's comment. $\endgroup$
    – Tom
    Aug 4 '18 at 17:39
  • 1
    $\begingroup$ The last two are 'units' equations, with time in seconds given as $N/kgms^{-2}$. Not sure how friction, pressure and time are related though... $\endgroup$ Aug 5 '18 at 9:21
  • 1
    $\begingroup$ All have "n". And the teacher said All Caps are OK $\endgroup$
    – DrD
    Aug 5 '18 at 10:10


They are equations for unit prefixes


$ f = \mu n$, $f$(femto), $\mu$(micro), $n$(nano),
$f = 10^{-15}$, $\mu = 10^{-6}$, $n = 10^{-9}$, $\mu n = 10^{-15}$ thus, $f = \mu n$

Line 2:

$Pa=\frac{n}{m^2}$, $P$(peta), $a$(atto), $n$(nano), $m$(milli),
$Pa = 10^{15} 10^{-18} = 10^{-3}$, $\frac{n}{m^2} = \frac{10^{-9}}{(10^{-3})^2} = 10^{-3}$, thus $Pa=\frac{n}{m^2}$

Line 3:

$T=\frac{n}{am}$, $T$(tera), $n$(nano), $a$(atto), $m$(milli),
$T=10^{12}$, $\frac{n}{am} = \frac{10^{-9}}{10^{-18}10^{-3}} = 10^{12}$, thus $T=\frac{n}{am}$

  • 1
    $\begingroup$ Good find. Multi-line/-paragraph spoilers are a bit tricky. You have to prefix each line of the block with >! and you must introduce line breaks manually with the <br /> tag ior with two or more spaces at the end of a line. But I think that the current markup with a spoiler block for each formula is fine. $\endgroup$
    – M Oehm
    Aug 5 '18 at 18:46

Well, I guess it should be me to get things started with a partial answer identifying the more famous equations these are not:

$f=\mu n$ is not

$F=\mu N$, the formula for kinetic friction, where

$F$ is the magnitude of the force caused by friction
$\mu$ is the coefficient of friction, and
$N$ is the magnitude of the normal force.

$Pa=\frac{n}{m^2}$ is not

$Pa=\frac{N}{m^2}$, the definition of a pascal (the SI unit of pressure) as being one newton per square meter.

$T=\frac{n}{am}$ is not

$T=\frac{N}{Am}$, the definition of a tesla (the SI unit of magnetic flux density) as being one newton divided by an ampere-metre.

(In all of the above non-answers, notice how the puzzle topic has forced me to painstakingly write all the scientists' names without a capital letter, because that's how you are supposed to do it when those names are used as units.)

The actual purpose of the equations coming up as soon as I figure them out :-)
(Probably better not to start holding your breath though..)


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.