Answer to the Question 08/04

FALLING MAGNET

The question was:





Bar magnet falling in a vertical copper pipe quickly reaches "terminal" velocity and stops accelerating. Find that velocity as a function of the features of the magnet and the pipe.


(10/05) It has been brought to our attention that this problem has been recently considered in great detail by J. Iniguez, V. Raposo, A. Hernadez-Lopez, A. G. Flores and M. Zazo in a paper published in European Journal of Physics 25 593-604 (2004). A copy of this paper can be found in the PDF file. In that paper a great care has been taken to achieve an accurate quantitative prediction. One of the authors provided us with a short summary of the solution that can be found in the PDF file.


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