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# Should I always write units in equation no matter if it looks like variable?

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I am not sure if it is suitable in the site. I am asking the question here cause Olin and Celtschk said it here.

They told me to use unit in every "single line" (Nope! They didn't say like it. Olin said to always separate number and units. And Celtschk said to write units in middle lines).

I was doing a simple problem, and I noticed units may disturb my equation.

$$S=ut+\frac{1}{2}at^2$$

I am just putting a random value in $a$ and $t$

$$S=5u+\frac{1}{2} \cdot 2 \ ms^{-2} \cdot 5 \ s$$

I can write that

$$S=5u+\frac{1}{2}\cdot 10 \ ms^{-1}$$

In these equations, ms^{-1} is looking like a value (like as $u$) rather than unit. But if I had put a number instead of $u$ than the equation might look better. But when there's variable the units isn't looking better. What to do in these cases?

Why does this post require moderator attention?
Why should this post be closed?

In general, or with Mathjax? (2 comments)

# Comments on Should I always write units in equation no matter if it looks like variable?

BTW, I now notice that you incorrectly inserted. If you insert $5\\,\mathrm t$ into $ut$ you do *not*...
celtschk‭ wrote 12 months ago:

BTW, I now notice that you incorrectly inserted. If you insert $t=5\,\mathrm s$ into $ut$ you do not get $5u$, but $u\cdot 5\,\mathrm s$. Also, $t^2$ should become $(5\,\mathrm s)^2$. As a result, in your initial equation, $S$ equals a length, while in your final equation, $S$ equals a velocity.

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