It is the moment and I was indeed ignoring the weight of the bar itself since it shouldn't have influence on the system equilibrium.
Thanks a lot for that explanation. it's very helpful.
There's something I struggle to understand.
In the picture I attached to this post , the first drawing is a system with the sum of momentum = 0 (equilibrium).
In the second drawing I increase temporarily the force on point A in order to get and angle of 20° compare to the last position and...