Answer
$F_a=9680N$
Work Step by Step
$P_i+\frac{1}{2}\rho V_i^2+\rho gy_i=P_o+\frac{1}{2}\rho V_o^2+\rho gy_o$
$P_i-P_o=\frac{1}{2}\rho V_o^2=\frac{F_a}{A_r}$
$F_a=\frac{1}{2}\rho(V_o^2)A_r$
$F_a=\frac{1}{2}(1.29\frac{kg}{m^3})(180\frac{km}{h}\frac{1h 1000m}{3600s 1km})(6.0m^2)=9680N$