Measuring moment of inertia constants using rolling motion of common household objects

Abstract This study explores a simple, low-cost experimental method for determining the rotational inertia constant ( β ) using the rolling motion of everyday objects on an inclined plane. Four objects with distinct geometries—a bouncy ball, battery, ping pong ball, and cardboard core—were analysed by measuring their rolling times over a 0.4 m incline set at a 7.7° angle. The experimental values ( β ex ) were calculated and compared to their respective theoretical values ( β th ) derived from classical mechanics. The battery ( β ex = 0.48) and ping pong ball ( β ex = 0.64) closely matched their theoretical predictions (0.5 and 0.67), while the bouncy ball exhibited a large discrepancy ( β ex = 0.32) due to energy losses from bouncing. The cardboard core was modelled in two ways: as a thin-walled hollow cylinder ( β th = 1 ) and a thick-walled cylinder ( β th = 0.91 ). The latter provided a better fit to the experimental data, reducing the error from 10.05% to 1.15%, highlighting the importance of realistic modelling. Additionally, a graphical method—plotting t 2 versus 1 sin θ —was applied to the battery and yielded β = 0.515 , in excellent agreement with theory. These results illustrate the potential educational value of combining hands-on experiments with model evaluation and data analysis, offering a practical approach to enhance students’ understanding of rotational dynamics and the limitations of idealised physical models. The experiment is highly replicable in classroom settings, requires only household objects and basic tools, and supports inquiry-based physics learning in resource-limited environments.