The spin of a gyroscope that undergoes Thomas precession seems to change its direction without any torque, which would mean that conservation of angular momentum is violated. To resolve this paradox, it is shown that the spin dynamics equation describing Thomas precession (the BMT equation) can be written in terms of a torque applied to the spin. A simple method of finding an explicit expression for the torque is presented in the case of a gyroscope performing circular motion. An unexpected oscillatory character of the torque is explained in terms of the difference between the proper spin and the spin observed in the laboratory frame.
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2015
American Association of Physics Teachers
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