The physics professor had just finished his lecture about the pendulum, wherein he had shown the mathematical proof that an untouched pendulum will always swing in ever-decreasing arcs.
He then asked for a volunteer to demonstrate this fact by standing against a wall with a pendulum bob against his chin, then releasing the bob and allowing the pendulum to swing naturally through its arc. The professor reminded the class that the bob would return to, but not quite touching, the chin. No one volunteered. Although the science students “believed” that this
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