A particle is moving in the x-y plane. At certain instant of time, the components of its velocity and acceleration are as follows: $v_x=3{\mathrm{ms}}^{-1}$, $v_y=4{\mathrm{ms}}^{-1}$, $a_x=2{\mathrm{ms}}^{-2}$ and $a_y=1{\mathrm{ms}}^{-2}$. The rate of change of speed at this moment is