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Mechanical apparatus for the fold catastrophe demonstration

Authors: Manuel Fiolhais, Bojan Golli, Rogério Nogueira

Ref.: Eur. J. Phys. 42, 045001-1-045001-11 (2021)

Abstract: We present and discuss a non-expensive mechanical experiment which is very suitable for a classroom demonstration of the fold catastrophe behaviour. The apparatus consists of a bar attached to a pulley, to which a hanging body is connected by means of a thread wrapped around its rim. The system may perform stable oscillations or, else, the body may continuously fall down, while the pulley executes a sequence of 360° rotations. This behaviour is analysed in connection with the shape of the potential, which is a good example of a fold catastrophe potential. For the system to perform stable oscillations, that shape reminds a clothes washboard, with local maxima and minima, a potential well known in superconducting quantum computing. We provide some hints for the instructor to explore the device in lab classes. Paper selected for the EJP Highlights of 2021 collection.

DOI: https://doi.org/10.1088/1361-6404/abf059

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