he speed (and from it the momentum) of the ball and pendulum just after the collision is computed by assuming that the kinetic energy of the ball and pendulum just after the collision is totally converted into gravitational potential energy at the top of its swing. this requires that the frictional forces on the ball and pendulum system during the swing are small (negligible). the increase in gravitational potential energy is just the weight of the pendulum times the change in height, and the change in height can be computed from the maximum angle of the pendulum swing and some straightforward trigonometry. since the pendulum is not a point mass, the change in potential energy is given by the change in height of its center of gravity. the center of gravity can be located by removing it from its support screw at the top and then balan