A radial gate, $2$ m in width, hinged about a horizontal axis, closes the rectangular sluice of a control dam by the application of counterweight W $($see Fig Q$2$a$).$

i$)$ Determine the total hydrostatic force and its location on the gate relative to the surface.

ii$)$ For the gate to be stable, determine the force of the counterweight W $.$

iii$)$ Explain what will happen if the storage increases beyond a depth of $6$ m $.$

A siphon as shown in Fig. Q$2$b has a uniform circular bore of $75$ mm diameter and consists of a bent pipe with its crest $1\mathrm{.}8$ m above water level discharging into the atmosphere at a level of $3\mathrm{.}6$ m below the water level. Given the atmospheric pressure is equivalent to $10$ m of water, and neglecting losses due to friction, calculate:

i$)$ the velocity and discharge from the siphon;

ii$)$ the absolute pressure at point $B$