The mass of electron is $9.11\times {10}^{-31}\mathrm{kg},$ Planck constant is $6.626\times {10}^{-34}\mathrm{Js},$ the uncertainty involved in the measurement of velocity within a distance of $0.1{\mathrm{A}}^{\mathrm{o}}$ is

By Heisenberg's uncertainty principle,

$\begin{array}{l}\mathrm{\Delta p}\times \mathrm{\Delta x}=\frac{\mathrm{h}}{4\mathrm{\pi }}\mathrm{or}\mathrm{\Delta v}\times \mathrm{\Delta x}=\frac{\mathrm{h}}{4\mathrm{\pi m}}\\ \mathrm{Given}\mathrm{that},\mathrm{\Delta x}=0.1\stackrel{\mathrm{o}}{\mathrm{A}}=0.1\times {10}^{-10}\mathrm{m}\\ \mathrm{m}=9.11\times {10}^{-31}\mathrm{kg}\\ \mathrm{h}=\mathrm{Planck}\text{'}\mathrm{s}\mathrm{constant}\\ =6.626\times {10}^{-34}\mathrm{Js}\\ \mathrm{\pi }=3.14\\ \mathrm{Thus},\\ \mathrm{\Delta v}\times 0.1\times {10}^{-10}=\frac{6.626\times {10}^{-34}}{4\times 3.14\times 9.11\times {10}^{-31}}\\ =5.785\times {10}^6{\mathrm{ms}}^{-1}=5.79\times {10}^6{\mathrm{ms}}^{-1}\end{array}$