A horizontal $300-mm$ pipe in diameter and $420$ m long has a wall thickness of $1$ cm $.$ The

pipe is commercial steel and carries water from a reservoir to a level $100$ m below and dis$-$

charges into the air. Through measurements, the water flow in the pipe is $560\frac{L}{s}.$ What is

the maximum water hammer pressure head that can be expected on the valve if it closes in a

$0\mathrm{.}50$ s period? Neglect longitudinal stresses.