Blackwood pendulum experiment and the conservation of linear momentum

By a simple modification of the commercially available ballistic pendulums (e.g., Cenco as well as Beck), we demonstrate that these pendulums are not conceptually and pedagogically suitable for performing the experiment to verify the Law of Conservation of Linear Momentum. With modified equipment, the discrepancy between the true velocity of the projectile ball and the velocity as obtained by performing the collision experiment is shown to be as large as 17% if improper concepts are used for the analysis of the experimental data. The correct analysis, without any assumption about the conservation of linear momentum, is shown to yield experimentally acceptable results to within a few percent.