Comment on ‘Pendulum: the partial and global approach’

The paper Pendulum: the partial and global approach combines a historic introduction to the theoretical treatment of pendulum motion with presentation of data from measurements on a single pendulum. This comment focuses on the presentation and analysis of experimental data, and how the use of dimensionless variables in graphs would make use of the mathematical properties, placing the single measurement in a more general context, including mass-independence and the isochronism (for small angles). The concept of ‘effective weight’ used by Coelho is then discussed in relation to inertial forces and the principle of equivalence between inertial and gravitational mass.