Rotating Pendula - Length Vs. Height

Purpose

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

Equipment

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

Suggestions

Accelerate slowly, then maintain constant angular speed.

Setup Time

10 min.

Images

d5-24

Description

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.◙

References

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