$\Delta x \times \Delta p _{ x } \geq \frac{ h }{4 \pi}$

$\Rightarrow 2 a _{0} \times m \Delta v _{ r }=\frac{ h }{4 \pi}(\text { minimum })$

$\Rightarrow \Delta v _{ x}=\frac{ h }{4 \pi} \times \frac{1}{2 a _{0}} \times \frac{1}{ m }$

$=\frac{6.63 \times 10^{-34}}{4 \times 3.14 \times 2 \times 52.9 \times 10^{-12} \times 9.1 \times 10^{-31}}$

$=548273\; ms ^{-1}$

$=548.273\; km\;s ^{-1}$

$=548\; km\; s ^{-1}$