Question

A positive point charge with a mass of 0.43 kg is placed on a string and hangs vertically. Another negative point charge is placed directly beneath this charge a distance of d. Due to its weight and the electric force, the tension in the string is 22.8 Newtons. The negative charge is then moved directly to the left of the charge and the charge on the string swings to some angle and comes to equilibrium. When the charge on the string is in equilibrium, the negative charge is 4 times further away from its initial position below the charge. With respect to the vertical, to what angle, in degrees, does the charge on the string swing?

Answer 1

" When the charge on the string is in equilibrium, the negative charge is 4 times further away from its initial position below the charge."

In general this is an application of Coulombs law with some gravity added to it.

The 22.8N comes from adding the force from coulombs law to the gravity force. Gravity is ,43*9.81N so the remainder is coulombs force. Coulombs force also goes as 1/d^2 so knowing the new "d" tells you the Coulomb force in the new position. That plus the gravity force is the total force. there is no motion so the net force is zero.