A gas flows with a velocity $v$ along a pipe of cross-sectional area $S$ and bent an angle of $90^{\circ}$ at a point $A .$ What force does the gas exert on the pipe at $A$ if its density is $\rho$ ?
(a) $\frac{\sqrt{2} S v}{\rho}$
(b) $\sqrt{2} S v^{2} \rho$
(c) $\frac{\sqrt{3} S v^{2} \rho}{2}$
(d) $\sqrt{3} S v^{2} \rho$