A heavy horizontal cylinder of diameter $D$ supports a mass of liquid having density $\rho$ as shown in the figure. Find out the vertical component of force exerted by the liquid per unit length of the cylinder if $g$ is the acceleration due to gravity.
- $\frac{\pi D^{2}}{4} \rho g$
- $\frac{\pi D^{2}}{8} \rho g$
- $\frac{\pi D^{2}}{2} \rho g$
- $\frac{\pi D^{2}}{3} \rho g$
