Abstract
In this paper, the expressions for the forees acting on a boly placed in a two-imensional jet of an incompressible perfect fluid are obtained by the principle of momentum, under the assumption that the body under consideration has, on its surface, only some angular points with finite angle, if any, but no cusps at all. The obtained expressions for the forces are quite simple and elegant, and the result is applicable to all bodies having no cusps whatever on their surfaces. In the next place, the forces which will be experienced by a cylinder with rectangular cross-section placed in a jet of a perfect fluid are calculated by making use of BLASWS' formula and it is shown that the expressions for the forces thus deduced are, as we should expect, exactly the same as those far the forces acting on any body, obtained in a general manner by employing the principle of momentum
