Wilberforce pendulum: Oscillates between rotation and up-down.

Wilberforce pendulum. This apparatus is designed so that the period of the up and down oscillation is nearly equal to the period of the torsional oscillation. Slowly the apparatus switches between pure up and down mode to pure torsional mode. Note: The model in Pimentel has a 4' spring and a much longer period (~15 sec). The tabletop model can be provided on request.
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Demo Diagram: