Swinging Rod (1.19-A) - A Preview

Investigating the period, motion, and moment of inertia of the pendulum and its underlying principle.


Pendulums come in various forms and varieties. Here we introduce a swinging rod whose pivot could be changed. Does the time period change and how? Could you build a theoretical model, invoking some basic concepts in mechanics and angular motion? This experiment typifies the exercise of observing a natural phenomenon and finding an underlying principle that explains the observation. In the end, the prediction and outcomes are compared.


• Mathematical model of a simple swinging rod.
• Investigating period, motion, and moment of inertia.
• Application of the parallel axis theorem.
• Comparing theoretical predictions with experimental observation.
• Calculating uncertainties.

How does it work?

In this experiment, the object of interest is a rectangular wooden rod, specifically, a meter rule of mass M and length L. The rod can be hung on to a pin pivoted on a firm post. To experiment with different moments of inertia, there is a series of holes drilled through the midline of the rod.

As shown in the figure, the position of the pin is P and the rod is made to swing in a vertical plane about this pivot. The center of mass is, of course, the geometric center of the wooden rod, point O.
Students are required to measure the time period T of the oscillation with a stopwatch as the pivot P is varied and plot a graph between T and d = OP. These observations are analyzed for uncertainties and compared with the mathematical model.


Parts Included

  1. Stand
  2. Rod holder
  3. Rod
  4. Stopwatch

You can get the PDF version of the brochure by clicking on this link.