On the derivation of Coulomb's law It is said in the book that Coulomb's electric pendulum experiment is more powerful than the torsion pendulum experiment in proving the inverse square law, but how Coulomb deduces the relationship between Coulomb force and R through the relationship between the pendulum period T and the distance r between two charge spheres? It is best to list the relevant derivation formula, thank you!

On the derivation of Coulomb's law It is said in the book that Coulomb's electric pendulum experiment is more powerful than the torsion pendulum experiment in proving the inverse square law, but how Coulomb deduces the relationship between Coulomb force and R through the relationship between the pendulum period T and the distance r between two charge spheres? It is best to list the relevant derivation formula, thank you!

Coulomb's law is not a formula derived, it is a rule summed up by Coulomb according to the experimental data