If an element of area DS is located horizontally at a depth h below the surface of a liquid, the force acting downward on it equals the weight of
the column of liquid above DS. Thus if the density of the liquid is r, this weight is F/rhDS. Pascal’s law asserts that this force is independent of the orientation of the element of area DS so it may be horizontal, vertical or at an arbitrary inclination, and the fluid force will be the same. Forces due to
liquid pressure are called hydrostatic forces, and the force per unit area F /DS is called the hydrostatic pressure in the liquid at the depth h . This means that if the element of area is completely immersed in liquid, the forces on either
side of it will be equal and opposite. If, however, DS only has liquid on one side, the hydrostatic force will not be balanced by an equal and opposite one
on the other side.