Water supply

A chemical plant requires a water supply of 12m^3/hr. Suppose the rate of flow in the water pipe is 2m/sec. Find the radius of the pipe to be used in centimeters.

Velocity
$v = 2 ~ \dfrac{\text{m}}{\text{s}} \times \dfrac{3600 ~ \text{s}}{1 ~ \text{hr}} = 7200 ~ \text{m/hr}$
 

Discharge, Q = Velocity, v × Area, A or
$Q = vA$

$12 = 7200 \times \pi r^2$

$r = 0.023 ~ \text{ m} = 2.3 ~ \text{ cm}$