If a body is floating on the surface, the hydrostatic upthrust, as well as being equal to the weight of fluid displaced, is also equal to the weight of the body.
If the object were not in the fluid, the space the object occupied would be filled by fluid having a weight w fl . This weight is supported by the surrounding fluid, so the buoyant force must equal w ...If the object were not in the fluid, the space the object occupied would be filled by fluid having a weight w fl . This weight is supported by the surrounding fluid, so the buoyant force must equal w fl , the weight of the fluid displaced by the object. In other words, the force due to the pressure at the bottom is pointed up, while at the top, the force due to the pressure is pointed down; the forces due to the pressures at the sides are pointing into the body.
One mistake you see in solutions to submerged-object static fluid problems, is the inclusion, in the free body diagram for the problem, in addition to the buoyant force
