February 2020 issue of AJPFebruary 2020 Issue,

Volume 88, No. 2


A uniform explanation of all falling chain phenomena

The many variants of falling chain problems that have been published in the physics literature over the last two centuries are here analyzed using generalized Euler–Lagrange equations that include momentum flux. Familiar results are recovered, and new ones are presented. We demonstrate and clarify the role played by momentum flux by considering the falling chains as both variable-mass and fixed-mass systems. We calculate the evolution of energy as a useful parameter that provides insight into some of the unexpected behavior of falling chain systems. Our Lagrangian approach incorporates all published falling chain phenomena (including the whiplash effect) within a unifying framework, highlighting connections between the phenomena and providing a valuable pedagogical example of variable mass systems analysis.



Preparing students for the 21st century: Physics is the perfect playground by Kathleen T. Foote. DOI: 10.1119/10.0000370


Approximate early and often by Sanjoy Mahajan. DOI: 10.1119/10.0000507


A uniform explanation of all falling chain phenomena by Mark Denny. DOI: 10.1119/10.0000304

Low-cost nonlinear optics experiment for undergraduate instructional laboratory and lecture demonstration: A second experiment by Marlon S. Ribeiro, Karen C. Ribeiro, Sergio L. Gómez, Vinicius M. Lenart and Rozane de F. Turchiello. DOI: 10.1119/10.0000298

Composite cores and tamper yield: Lesser-known aspects of Manhattan Project fission bombs by B. Cameron Reed. DOI: 10.1119/10.0000035

Subharmonic frequency response in a magnetic pendulum by Yao Luo, Wenkai Fan, Chenghao Feng, Sihui Wang and Yinlong Wang. DOI: 10.1119/10.0000038

On the optimization of dissipative chain events by Renu Raman Sahu, Rishabh Nain and Vijay A. Singh. DOI: /10.1119/10.0000297

Simultaneity in cylindrical spacetime by Chunghyoung Lee. DOI: 10.1119/10.0000002

Optical absorption, scattering, and multiple scattering: Experimental measurements using food coloring, India ink, and milk by Frank Lamelas and Sudha Swaminathan. DOI: /10.1119/10.0000280


Conceptual difficulties in interpreting the real image of an object by Mićo M. Mitrović, Branislava M. Misailović, Biljana Z. Maksimović and Andrijana A. Žekić. DOI: 10.1119/10.0000520


Making sense of the divergent series for reconstructing a Hamiltonian from its eigenstates and eigenvalues by Carl M. Bender, Dorje C. Brody and Matthew F. Parry. DOI: /10.1119/10.0000215


A simple digital phase-sensitive detector using AVR microcontroller by Mehbub A. K. Nooruddin and Subhasish Roy. DOI: 10.1119/10.0000376


Implementation of the two-dimensional electrostatic particle-in-cell method by D. F. Rodríguez-Patiño, S. Ramírez, J. S. Salcedo-Gallo, J. H. Hoyos and E. Restrepo-Parra. DOI: 10.1119/10.0000375


American Journal of Physics 88, 168 (2020); https://doi.org/10.1119/10.0000465

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