# Question #ddb9e

$S = u t + \frac{a {t}^{2}}{2}$ if acceleration is constant.
$S = \frac{u + v}{2}$
And $v = u + a t$
So $S = \frac{u + u + a t}{2}$
Which gives us $S = u t + a {t}^{2} / 2$