A 20 g copper block is suspended by a vertical spring causing 1 cm elongation over the natural length of the spring. If a beaker of water is placed below the block so that the copper block is completely immersed in the liquid, the elongation of the spring is (Density of copper 9000 kg m\(^{-3}\), Density of water 1000 kg m\(^{-3}\), \( g = 10 \) ms\(^{-2}\)):