d
Change in momentum in vertical direction in time $\mathrm{t}=$ momentum final$-$momentum
initial in vertical direction $=-\rho L V t$
Change in momentum in horizontal direction in time $\mathrm{t}=$ momentum final$-$momentum
initial in horizontal direction $=\rho L V t$
So net change in momentum in time $\mathrm{t}=\sqrt{(\rho L V t)^{2}+(\rho L V t)^{2}}=\sqrt{2} \rho L V t$
Force $=$ Change in momentum per time $=\sqrt{2} \rho L V$