$4\mathrm{.}10$ A simple shower for remote locations is designed with a

cylindrical tank $500$ mm in diameter and $1\mathrm{.}800$ m high as

shown in Fig. P$4\mathrm{.}10.$ The water flows through a flapper

valve in the bottom through a $75-mm-$diameter opening.

The flapper must be pushed upward to open the valve.

How much force is required to open the valve?

$($a$)$ General view of shower tank

and valve

Force applied

to open valve

$($b$)$ Detail of valve

FIGURE P$4\mathrm{.}10$ Shower tank and valve for Problem $4\mathrm{.}10.$