A fluid mechanics question, please help.

Question

A vertical rectangular gate, 3m wide and 2m high is hinged at H.
On the left side of the gate, sea water lies up to a height 1.2m above the top of the gate.
Whereas on the right side of the gate, water is available up to a height touching the top of the gate.

Determine the horizontal force at the top of the gate, which is required to open it, F_A

 

[Given: Pwater = 1000 kg/m³ & Psea water = 1050 kg/m³]

 

DIAGRAM HERE: https://i499.photobucket.com/albums/rr354/sdsdasdsdsdsdsd/Flu_zps1rhhtspz.jpg

I'm definitely stumped. My answers don't add up. :(
Thank you for your time.

Answer 1

Hint, the moment 2F_A has to be greater than the opposite moment exerted by sea water -fresh water. see

http://www.geo.hunter.cuny.edu/~hsalmun/intro2fm07web/lectures/chapter2_2.pdf for details

 

Jim