Determination of the Unperturbed Period of a Torsion Pendulum in the Time-of-Swing Method

A symmetric disc-shaped torsion pendulum was designed to study the nonlinear effects of the torsion fiber. It was showed that the period of the pendulum decreases with the amplitude of the oscillation. Determination of the unperturbed period through a fit to measured data of the period variation with amplitude shows that this systematic error in the measurement of Newtonian gravitational constant G by the time-of-swing method can be reduced by an order of the magnitude at least.