The angular velocity of an electron occupying the second Bohr orbit of  $H{e}^{+}$ ion is $\left(in{\sec }^{-1}\right)$

Velocity of an electron in $H{e}^{+}$  ion in an orbit ($\upsilon$ )
    $=\frac{2\pi {\rm Z}{e}^2}{nh}\mathrm{......}\left(i\right)$
Radius of $H{e}^{+}$ ion in an orbit  $\left(r_n\right)=\frac{n^2{h}^2}{4{\pi }^{2}m{e}^2{\rm Z}}\mathrm{........}\left(ii\right)$
By equation (i) and (ii), we get
Angular velocity  $\left(\omega \right)=\frac{\upsilon }{r_n}=\frac{8{\pi }^3{{\rm Z}}^{2}m{e}^4}{n^3{h}^3}$
 $=\frac{8\times {(22/7)}^3\times {\left(2\right)}^2\times (9.108\times {10}^{-28})\times {(4.803\times {10}^{-10})}^4}{{\left(2\right)}^3\times {(6.626\times {10}^{-27})}^3}$
  $=2.067\times {10}^{16}{\sec }^{-1}$