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*Pendulum* systems may be [modeled|kb:Modeling techniques] in [SAP2000|sap2000:home] using nonlinear [time-history|kb:Time-history analysis] analysis with large deflections. Typically, the restoring force comes from a linear spring modeled either as a torsional spring at the support or as a horizontal spring attached to the free end. Pendulum systems may be useful for simulation and solution of isolation and [tuned-mass damper|tutorials:Tuned-mass damper] problems.

As shown in Figures 1 and 2, a {link-window:http://en.wikipedia.org/wiki/Newton%27s_cradle}Newton's cradle {link-window} pendulum system is modeled using axially stiff [frame|kb:Frame] objects and gap (compression-only) [links|kb:Link], located at the points of contact. Attached is an animation of the system oscillating.

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!Pendulum_1.png|align=center,border=1!

{center-text}Figure 1 - Newton's cradle pendulum system{center-text}

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!Pendulum_2.png|align=center,border=1!

{center-text}Figure 2 - Newton's cradle pendulum system{center-text}


h1. See Also

* [Contact surface|kb:Contact surface] article


h1. Attachments

* [Pendulum video |Pendulum^Pendulum_video.zip] (zipped AVI file)

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*TO DO:* Upload model for test problem with pendulum (by Rob).
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