With a partner, I both built and measured a trifilar pendulum. This device is a torsional pendulum with three strings. When it is displaced, the ratio of the mass of the object placed on the platform to it's moment of inertia will cause the system to oscillate with a specific frequency. Through measuring the mass of the object and the period of rotation, the moment of inertia can be precisely determined. Additionally, we investigated the role of damping in error and performed an error analysis on our results.
This project had three major components.
1. Physical System: The pendulum itself is constructed from banister rails, laser cut acrylic disks and Kevlar spear fishing line, chosen due to very low stretch under load.
2. Measurement System: The measurements for this system needed to be very precise. This is frequently done through timing multiple periods of oscillation. However, we also wanted to determine the damping coefficient of the system, so we also needed to have position data. Therefore, we built a custom quadrature encoder that read slots cut into the platform. This gave us very precise and accurate data.
3. Theoretical Calculation and Error Analysis: Once we calculated the measured moment of inertia from the period of the measurement, we compared it to a theoretical calculation and determined both the factors in our measurements that caused our errors and the factors in our mathematics that affected them. Further analysis can be found in the linked report.