In a steady and incompressible flow of a fluid (density = $1.25\: kg\: m^{-3}$), the difference between stagnation and static pressures at the same location in the flow is $30 \:mm$ of mercury (density = $13600 \:kg \:m^{-3}$). Considering gravitational acceleration as $10 \:m \:s^{-2}$ the fluid speed (in $m \:s^{-1}$) is _________________