Physical Pendulum Damped by Dry Friction

Abstract In this work, pendular movement damped by dry friction was studied. Dry friction differs from viscous friction by: a) the amplitude of oscillation linearly decays, whereas in the viscous damping the oscillation decays exponentially; b) the frequency of oscillation is keeping in presence of dry friction, however, the frequency of oscillation is reduced due to damping factor in viscous case. Some experiments were performed using a wood clapboard suspended and oscillating in lateral contact with a flat plate and using a DVD suspended by an axis stuck on its edge, where the friction was in this axis. The movements were recorded an analyzed with aid of software Tracker. It was possible to obtain decay parameters and friction force in both cases. Also, viscous damping forces were calculated due to drag from the air and showed to be negligible with respect to dry friction.