a
\(\%\) error in velocity \(=\frac{\Delta V}{V} \times 100\)

\(\therefore 0.001=\frac{\Delta V}{300} \times 100\)

\(\Rightarrow \Delta V=3 \times 10^{-3}\)

According to Heisenberg uncertainty principle,

\(\Delta x \cdot m \Delta V \geq \frac{h}{4 \pi}\)

\(\Rightarrow \Delta x=\frac{h}{4 \pi m \Delta V}\)

\(\Rightarrow \Delta x =\frac{6.63 \times 10^{-34}}{4 \times 3.14 \times 9.10^{-31} \times 3 \times 10^{-3}}\)

\(=1.92 \times 10^{-2} \mathrm{\,m} \)