A mass of 1 kg is suspended from a spring of force constant 400 N ,...

$T=2 \pi \sqrt{\frac{m}{R}}=2 \pi \sqrt{\frac{1}{400}}=\frac{2 \pi}{20}$ Frequency $n=\frac{20}{2 \pi} \omega=2 \pi n=2 \pi \times \frac{20}{2 \pi}=20$ Total energy $$\begin{aligned}& E=\frac{1}{2} m \omega^2 r^2 \& 2=\frac{1}{2} \times 1 \times 400 \times r^2\end{aligned}$$\begin{gathered}r=\frac{1}{10} \mathrm{ m} \\ \text{ Acceleration }=\omega^2 r=400 \times \frac{1}{10}=40 \mathrm{ m} / \mathrm{s}^2\end{gathered}$