Calculating Moments of a Tank of Water

Nov 2019
Hello all,

I was hoping someone could help me calculate the moment a tank wall experiences.

I have the following question:-

Tank contains water with dimensions:
4m Wide
12m Long
3m Tall

Determine the moment at the bottom of the long side at its centre.

I have drawn a sketch of the tank and highlighted in dark what I believe is the "bottom of the long side"


To calculate the force acting on the wall (12 x 3) I have done the following:-

F = p * g * a * y
p = density of water (1000)
g = gravity (9.81)
a = area (36)
y = distance from the top of the tank to the walls centroid (1.5)

1000 * 9.81 * 36 * 1.5 = 529740 N of force acting on the wall.

I am not really sure where to go from here?

Can anyone help?
Oct 2017
Use the other formula! The one you've used here is for an object suspended in the middle of it.