wudnt u add the weight of the barge too to the downward force??
1650sinx + 40,000 = 1800sin20??
nope, nid's rite, cuz she has considered the forces acting on the barge, while the weight is the force of the gravity acting on the barge, the weight is balanced by the buoyance force acting on the barge by the water (obviously the boat and the barge will be in water
), just think as though the boat and the barge was on the ground, the normal force wud balance the weight of the barge and in this case the buoyance force does that