Welcome back! Physics PhD student Subhayan Sahu returns this week for another installment in our series highlighting oscillation demonstrations. This week’s highlight: Demonstration G1-14 Pendula With Different Masses. Check out his video below:


These swinging cubes are made of a variety of materials, from aluminum to lead. We can see that for a simple pendulum swinging under gravity, the period is dependent only on the length. So long as these pendula all have the same length, they have the same period!


You can try this for yourself in the PhET Collection’s Pendulum Lab simulation. In the lab, create two pendula with the same length and mass. Pause the simulation while you position them to the same height and release; you’ll see they have the same period. Now reduce the mass of one while keeping the mass of the other fixed; the period stays the same! Now try changing the length of one pendulum to see how that changes the period.