I have the below problem followed by the answer I believe it to be. Would somebody be able to confirm I have got it right as I am not sure??

Hinged water storage is shown below. Its top side is denoted as C, the narrow side as B and the long side as A. Assume water density is 1000 kg/m3 and gravity is 9.81 m/s2 Side A is hinged at the bottom edge and secured using a clasp at its top edge. Dimensions are: L = 1m, H = 0.5m & W = 0.5m

When the tank is full of water:

a) Calculate the required resisting force at the clasp to keep the panel shut.

ANSWER:

Here force along depth of A is varying continuously, so there are 3 forces on tank side.

H=0.5

L=1

W= 0.5

A=0.5m2

y =0.25

1st moment of area =

Area * y = 0.5 *0.25 = 0.125

2nd moment of area =

Iss = Iyy +A(y) 2 = BD3 /12 + BD (y)2

=1* (0.5)3 /12 + 1*0.5 *(0.25)2

=0.04

Center of pressure:

= 2nd moment / 1st moment = 0.04 / 0.125 = 0.328

Total Thrust force

= ρ*g*A* y

= 1000*9.8*0.5*0.25 = 1225 N

The resisting force on the clasp F2.

Resistive Force x Distance from Hinge = Clasp Force x Distance from Hinge

F1 D1 = F2 D2

1225* 0.3 = F2 *0.5

F2 =1225* 0.3 / 0.5

=735 N

( F3 is the Hinge Force = F2 - F1 =1225 -735 = 490 N )