Consider 3rd orbit of ${\mathrm{He}}^{+}$ (Helium), using non-relativistic approach, the speed of electron in this orbit will be $[\mathrm{given} \mathrm{K}=9\mathrm{x}{10}^9$ constant,  Z = 2 and h (Planck's Constant) $\left.=6.6\times {10}^{-34} \mathrm{J} \mathrm{s}\right]$

Energy of electron in $H{e}^{+}$ 3rd orbit 

$E_3=-13.6\times \frac{{\mathrm{Z}}^2}{n^2}\mathrm{eV}=-13.6\times \frac{4}{9}\mathrm{eV}$

       $=-13.6\times \frac{4}{9}\times 1.6\times {10}^{-19} \mathrm{J}\simeq 9.7\times {10}^{-19} \mathrm{J}$

As per Bohr's model,

Kinetic energy of electron in the 3rd orbit = - $E_3$

$\therefore 9.7\times {10}^{-19}=\frac{1}{2}{m}_e{v}^2$

$v=\sqrt{\frac{2\times 9.7\times {10}^{-19}}{9.1\times {10}^{-31}}}=1.46\times {10}^6 \mathrm{m}{ \mathrm{s}}^{-1}$