Simple Pendulum
A simple pendulum has a small-diameter bob and a string that has a very small mass but is strong enough not to stretch appreciably. The linear displacement from equilibrium is s, the length of the arc. Also shown are the forces on the bob, which result in a net force of −mgsinθ toward the equilibrium position—that is, a restoring force.
Source
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"OpenStax College, College Physics. October 8, 2012."
http://cnx.org/content/m42243/latest/?collection=col11406/1.7
OpenStax CNX
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