Motion of an object along a one-dimensional guide under elastic wave radiation reaction

We consider nonseparated motion of an object along a one-dimensional elastic guide (a beam or a string) under the radiated wave pressure. Conditions on the parameters of the vibration sources acting on the object and providing directional radiation are obtained. Using the exact solutions obtained under the assumption that the law of motion is uniform, we study the dependencies of the motive force and the vibration-source-to-object-translational-motion energy conversion factor (efficiency) on the body velocity. It is shown that an object moving at a supercritical velocity for the case in which only a single wave is excited to the left of it must be distributed; i.e., its dimensions must be comparable with the radiated wave length. In this case, the efficiency can be arbitrarily close to unity.