From Mechanics

\displaystyle \mathbf{F}=\text{ 24}00\mathbf{j}\ \text{N},\quad m=\text{125}0\ \text{kg},\quad \mathbf{u}=\text{ 15}\mathbf{i}\ \text{m}{{\text{s}}^{-1}}

\displaystyle \begin{align} & \mathbf{I}=m\mathbf{v}-m\mathbf{u} \\ & 2400\mathbf{j}=1250\mathbf{v}-1250\times 15\mathbf{i} \\ & \mathbf{v}=15\mathbf{i}+1\textrm{.}92\mathbf{j} \\ & v=\sqrt{{{15}^{2}}+{{1\textrm{.}92}^{2}}}=15\textrm{.}1\text{ m}{{\text{s}}^{\text{-1}}} \\ \end{align}