For the flash board shown in Fig. P$2\mathrm{.}15,$ find the depth of water H and the compressive force on the strut per metre length of the flash board when the board is about to trip.

$($Hint: At the time of tipping the centre of pressure coincides with the hinge$)$

Fig. $2\mathrm{.}89$ Problem $2\mathrm{.}32$