Finding the tension in a rope attached to a gate underwater.

[pressurised]

Homework Statement

2 & 3. The Attempt at a Solution
I've worked out:
The total force on the gate.
I have worked out the centre of pressure which I got a value of 10/3m (from the hinge).
For the moment about the hinge I got a value of 981,000Nm using the equation M=F_N*X where X is the centre of pressure and F_N is the total force on the gate. Dividing this by 5 (length of gate) I get 196,200N, which I assume must be T?

(Or T*cosθ which gives me 117,720N, which seems to small)

 

[pressurised]

Acutally, if I work out the moment M due to the force dF_N * the centre of pressure (metres from hinge), and equate this moment to the moment due to T:

294,300(10/3)=T(5)
T=196,200N

?

 

[pressurised]

Sorry, or do I equate the moment 294,300(10/3) in the downwards direction then it will equal T? So 294,300*(10/3)*(3/5)=T(5). So T=117,720N