A child stands on the edge of the cliff $10 \mathrm{~m}$ above the ground and throws a stone horizontally with an initial speed of $5 \mathrm{~ms}^{-1}$. Neglecting the air resistance, the speed with which the stone hits the ground will be $\mathrm{ms}^{-1}$ (given, $g=10 \mathrm{~ms}^{-2}$ ).