Damped Mechanical Oscillator: Experiment and Detailed Energy Analysis

• Published in: The Physics teacher 2014-02, Vol.52 (2), p.88-90
• Main Authors: Corridoni, Tommaso, D'Anna, Michele, Fuchs, Hans
• Format: Article
• Language: English
• Subjects: Energy; High Schools; Magnets; Measurement; Motion; Physics; Science Experiments; Science Instruction; Secondary School Science
• ISSN: 0031-921X; 1943-4928
• DOI: 10.1119/1.4862111

The damped oscillator is discussed in every high school textbook or introductory physics course, and a large number of papers are devoted to it in physics didactics journals. Papers typically focus on kinematic and dynamic aspects 1–5 and less often on energy. Among the latter, some are devoted to the peculiar decreasing behavior of energy characterized by ripples, 6,7 which can easily be demonstrated by using a dynamic modeling approach. 8 In this note we consider an oscillator consisting of a cart running on a horizontal track, two springs, and a damping device created with magnets and a metal plate attached to the cart (Fig. 1). Using sensors and data-acquisition software, 9 we measure kinematic quantities and three forces: those of the springs on the cart and, separately, the force between magnets and the plate. A detailed analysis of the energy exchanges between the cart and the interacting parts is obtained. In particular, we show that only the energy exchanges with the magnets are affected by dissipative processes while over a suitable time interval the net energy exchanged between cart and springs equals zero.