Swinging Atwood's Machine

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This Demonstration solves a system of two masses hanging from two pulleys, with one of them swinging and the other moving vertically, a system known as a "swinging Atwood's machine." The variables of the system are the angle and , the length of the string of the swinging mass, both depending on the time . Friction is neglected.

Contributed by: Enrique Zeleny (March 2013)
Open content licensed under CC BY-NC-SA



The equations of motion are



where is the gravitational acceleration.


[1] D. Morin, Introduction to Classical Mechanics with Problems and Solutions, New York: Cambridge University Press, 2008 pp. 15.

[2] Wikipedia. "Swinging Atwood's Machine." (Nov 26, 2012) en.wikipedia.org/wiki/Swinging_Atwood%27s_machine.

[3] D. Lu. Trajectories of the Swinging Atwood's Machine. [Video] (Apr 24, 2011) www.youtube.com/watch?v=oVsfdM9sacI.

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