\(m=1 \times 10^{-20} \,kg\)
\(T=1 \times 10^{-5} \,kg\)
Maximum speed \(=A \omega=1 \times 10^3 \,m / s \quad \dots (i)\)
\(\omega=\frac{2 \pi}{T}=2 \pi \times 10^5 \,rad / s\)
Putting value of \(\omega\) in \((i)\)
\(A \times 2 \pi \times 10^5=1 \times 10^3\)
\(A=\frac{1}{2 \pi \times 10^2}\)
\(A=1.59 \,mm\)