It is well known that the thrust deduction related to the prediction of power performance of a ship is rather resistance increase, and as a preliminary study forces acting on an object in a uniform flow of ideal fluid due to singularities located behind it are investigated. The propulsor and other devices in the stern region are approximated by exterior singularities and their effects upon the resistance increase are estimated by taking a circular cylinder and a sphere as the 2D and 3D body, respectively. The circle theorem is used to get the complex velocity potential for the flow field under consideration, and the Blasius theorem is applied to obtain forces acting on the circular cylinder. The Butler’s sphere theorem was made use of to find the Stokes’ stream function when the resulting flow is axisymmetric, and then the extended Lagally’s theorem, for which the proof is given in this work, to get the force acting on the sphere due to the singularity. This force is given in terms of two parameters, which are the separation distance between the object and the singularity, and the strength of the singularity. Assuming that the two non-dimensionlalized parameters are much smaller than one, the leading order terms approximation was obtained, and it is shown that the approximation by leading order terms are in good agreement with the exact formula for the region of small parameters considered. In the case of 2D, as singularities sinks, point vortices and dipoles and their combinations were treated. In the case of 3D, taking a dipole as singularity, the result showed that the effect of the image of the dipole with respect to the sphere is the most important, if the dimensionless separation distance and the square root of the dimensionless strength of the dipole are of the same order.