Correct answer is : 6
Total energy = K.E. + P.E.
at \(\mathrm{x}=0.04 \mathrm{~m}, \text{T.E.} =0.5+0.4=0.9 \mathrm{~J}\)
\(\mathrm{T} . \mathrm{E}=1 \mathrm{~m}\omega ^{2} \mathrm{A}^{2}=0.9\)
\(
=\frac{1}{2} \times 0.2\left(2 \pi \times \frac{25}{\pi}\right)^{2} \times \mathrm{A}^{2}=0.9
\)
\(\Rightarrow \mathrm{A}=0.06 \mathrm{~m}\)
\(\mathrm{A}=6 \mathrm{~cm}\)