JEE Main 2013 — Oscillations Question with Solution

A mass $m=1.0\mathrm{kg}$ is put on a flat pan attached to a vertical spring fixed on the ground. The mass of the spring and the pan is negligible. When pressed slightly and released, the mass executes simple harmonic motion. The spring constant is $500\mathrm{N}/\mathrm{m}$. What is the amplitude A of the motion, so that the mass $m$ tends to get detached from the pan ? (Take $g=10\mathrm{m}/{\mathrm{s}}^2$ ). The spring is stiff enough so that it does not get distorted during the motion.