A second pendulum (T = 2 s) consists of a charged metal ball of mass m = 16 g suspended on a thread whose mass can be neglected. When the pendulum was placed in the field of another ball, which had a charge of the opposite sign and was located under the suspension point at a large distance from the pendulum, the period of oscillation of the pendulum became equal to T = 1.6 s. Find the force of mutual attraction between the balls. Neglect changes in the distance between the balls and the direction of the force of electrical attraction.

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