Experimental dynamics of a physical pendulum descending an inclined plane

Abstract

Abstract

Abstract The dynamics of a physical pendulum coupled to a support descending an inclined plane with uniform acceleration are investigated experimentally. Although this configuration is a standard problem in advanced mechanics courses, its direct quantitative experimental validation has received little attention in the physics education literature. A low-cost, reproducible setup based on a cart and smartphone video analysis was employed to study the pendulum dynamics from both inertial and non-inertial reference frames; a key feature of the design is that a second smartphone was mounted directly onto the cart, enabling the observer to operate within the accelerated frame itself. The experimental results are consistent with the theoretical model and reveal a measurable decrease in the effective gravitational field, reaching 8% at the maximum inclination studied, providing a quantitative demonstration of the Equivalence Principle in a classical mechanical context. A systematic increase in the effective moment of inertia with inclination angle is also observed and attributed to inclination-dependent displacement of the suspension point, offering a natural framework for introducing the concept of effective parameters in real physical systems. The experiment thus constitutes a reproducible pedagogical resource for undergraduate instruction in coupled systems, non-inertial reference frames, and physical modelling strategies using accessible equipment.