In an impact-plate grain yield sensor mounted at the head of a combine clean-grain elevator, clean grain strikes an inclined impact plate at an approach velocity of $v_1 = 3.2\text{ m/s}$ and leaves with negligible normal rebound velocity. If the measured normal impact force on the load cell is $F_n = 48.0\text{ N}$, the instantaneous mass flow rate of grain $\dot{m}$ in $\text{kg/s}$ is ________ (answer in integer).