WOLFRAM|DEMONSTRATIONS PROJECT

Motion of Pendulum with Varying Length

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animation
drum radius
0.212
show trace
initial angular position
-40.
°
We consider a pendulum consisting of a bob hanging on a string attached to the top of a stationary cylindrical drum. When the pendulum is released from a position away from the vertical, it swings with a varying length, tracing a spiral-shaped path.
If the bob can swing to its maximum angle, it will reach its initial height (assuming there is no friction). This is a consequence of the conservation of energy.