Rotating Pendula - Length Vs. Height


To show that pendula of different length suspended from the same point rotating at the same angular speed rise to the same vertical height.◙


Base from rotating stool, rod, three golf balls on strings, and guide wires.


Accelerate slowly, then maintain constant angular speed.

Setup Time

10 min.




When the device is rotated at an angular speed w the angle a from the vertical which a pendulum of length l will assume is given by cos a = g / w^2 l, where g is the acceleration of gravity. The vertical distance of each from the support point is l cos a = g / w^2, the same value for each of the pendulum. This can be easily observed using the apparatus.◙


Richard E. Berg, Lecture Demonstration Analysis Sheet. Lee Larson and Roderick Grant, The Airplane Experiment, TPT 29, 564-565 (1991).