An Atwood machine with variable mass is presented in this work using a robust configuration that enables data acquisition from the dynamic oscillatory motion during a relatively long time interval. The system is easily implemented through the use of a pulley and a set of three bodies whose masses satisfy the relationship M>m1>m2, and M<m1 + m2. The problem can be treated in a playful way for high school students or with greater depth, using the Lagrangian formalism for undergraduate students. The oscillatory motion of the system is not similar to any of the cases of periodic or aperiodic damping reported in the literature, because the mass of the system changes with decreasing time intervals. Through the use of photogates (sensors) coupled to the pulley and Tracker Software it was obtained a set of dynamic variables to be compared with the expected results derived from the analytical description.
Atwood machine; dynamics; oscillatory motion; variable mass
