A mass of $2.0 \mathrm{kg}$ is put on a flat pan attached to a vertical spring fixed on the ground as shown in the figure. The mass of the spring and the pan is negligible. When pressed slightly and released the mass executes slightly and released the mass executes a simple harmonic motion. The spring constant is $200 \mathrm{N} {\mathrm{m}}^{-1}$. What should be the minimum amplitude of the motion, so that the mass gets detached from the pan? (Take $g=10$ $\mathrm{m}{\mathrm{s}}^{-2}$ )