Answer
0.094 m.
Work Step by Step
Use Poiseuille’s equation, 10-9, to find the radius. The diameter is double the radius.
$$Q=\frac{\pi R^4 (P_1-P_2)}{8 \eta \mathcal{l}}$$
$$ d=2R=2(\frac{8 \eta \mathcal{l}Q}{\pi(P_1-P_2)})^{1/4}$$
The flow rate Q is $\frac{(8.0m)(14.0m)(4.0m)}{900s}=0.4978\; m^3/s$.
The pressure difference is 73.13 Pa.
$$ d=2R$$
$$=2(\frac{8(1.8\times10^{-5}\;Pa \cdot s)(15.5m)( 0.4978\; m^3/s)}{\pi(73.13\;Pa)})^{1/4}$$
$$=0.094\;m$$
