Let the total energy of a particle executing simple harmonic motion with angular frequency is $1 \mathrm{rad} {\mathrm{s}}^{-1}$ is $0.256 \mathrm{J}$. If the displacement of the particle at time $\mathrm{t}=\frac{\mathrm{\pi }}{2} \mathrm{s}$ is $8\sqrt{2} \mathrm{cm}$ then the amplitude of motion is