The kinetic energy of an electron in the second Bohr orbit of a hydrogen atom is  ( $a_0$ is Bohr radius) 

$mvr=\frac{nh}{2\pi }$
$v=\frac{nh}{n\pi mr}$
$KE=\frac{1}{2}m{v}^2$
$=\frac{1}{2}m\left[\frac{n^2{n}^2}{4{\pi }^2{m}^2{r}^2}\right]$
$\text{But }r=\frac{a_O\times n^2}{Z}\text{for}{2}^{\text{nd}}\text{orbit,}r=\frac{a_O\times 4}{1}$
$\therefore KE=\frac{1}{2}m\left[\frac{4h^2}{4{\pi }^2{m}^{2}16{a_o}^2}\right] r=4a_o$
$K.E=\frac{h^2}{32{\pi }^{2}m{a_o}^2}$