Solution to task 304 from Chertov´s for extramural stud

Solution to task 304 from Chertov´s for extramural stud

304. Two equally charged balls are suspended at one point on threads of the same length. In this case, the threads diverged at an angle α. The balls are dipped in oil. What is the density ρ0 of the oil if the angle of divergence of the threads when immersed in oil remains unchanged? The density of the material of the balls is ρ = 1.5.103 kg / m3, the dielectric constant of the oil is ε = 2.2.