Abstract
Abstract After analysing results on the measurement of the acceleration of gravity using a physical pendulum in our teaching laboratory, we found that the value reported by the students is always higher than the theoretical expectations. In this article we analyze critically some of the students hypotheses for such displacement, and we perform an investigation of our own to detect what is leading to this result. We disregarded any flaw on the experimental procedure performed by the students, and instead, concluded that the miscalibration of the laboratory instruments was distorting the students measurements, leading to a ~5% increase in the calculated value of the acceleration of gravity.
Highlights
The analysis of the oscillatory behaviour of physical systems is a fundamental part of physics courses at the undergraduate level, where simple harmonic oscillators are studied, both from the theoretical and the experimental point of view.A very common experiment in fundamental physics courses, which has been used throughout the years, consists on the analysis of the oscillatory motion of a physical pendulum [1,2,3], which is generally used to get a measurement of the gravitational acceleration g
From the theoretical physics point of view, the physical pendulum can be used to understand the behavior of systems acted on restoring forces proportional to the displacement from the equilibrium point, the concept of a rigid body and the determination of its center of mass (CM) and moment of inertia, the use of Steiner’s theorem, the effect of damping, among others [4]
We present here our own investigation of the oscillatory motion of the physical pendulum, trying to figure out why such discrepancies appear in our experimental setup
Summary
The analysis of the oscillatory behaviour of physical systems is a fundamental part of physics courses at the undergraduate level, where simple harmonic oscillators are studied, both from the theoretical and the experimental point of view. A very common experiment in fundamental physics courses, which has been used throughout the years, consists on the analysis of the oscillatory motion of a physical pendulum [1,2,3], which is generally used to get a measurement of the gravitational acceleration g. In order to explain this discrepancy between their result and the known value of g, students give all kind of explanations: non-validity of the small angle approximation in their experiment, the use of a non-uniform rod (due to the holes drilled on it), the difficulty in finding the exact position of the CM, the presence of air currents in the laboratory producing unexpected effects, the oscillations of the rod not happening in a plane, to mention just a few.
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