Impulsive Motion of a System

Extract

In an article entitled “Two Problems on Impulsive Motion” (M. G., XLIV, p. 95) the writer (J. O’Keeffe) complains of the lack of method in elementary books on problems such as the initial motion of two jointed bars under the action of an impulse. In our view, such problems are best treated, in an elementary course, by reducing the total momentum of the system to a single linear momentum and a momentum-couple. The necessary equations are then obtained by using the principle of equivalence of this system with that of the impulses. This treatment makes it clear why and in what form it is correct to take moments about the point at which the bars are hinged. Below we give the general treatment, and also the application to this particular problem.