This apparatus was designed to provide data for sustained computations by engineering students in general physics and consists of a large pendulum swinging over a waxed-paper strip. The velocities of the ball at a number of positions are computed, the kinetic and potential energies are calculated for each position and plotted against the angle of displacement of the pendulum. The sum of the two curves when plotted is a horizontal line. Students interpret the total mechanical energy curve in terms of the conservation of mechanical energy. Student interest is motivated by the impressive size, visibility, and precision of the apparatus. The effectiveness of the demonstration is enhanced by using procedures simulating an engineering situation.