Two identical small charged spheres, each having a mass of 3X10^-2kg, hang at equilbrium. The length of the string is .2m, the angle between each string and the perpendicular is 10 degress. A=.034M
Because, angle of the string with the vertical (Q) = 10 degree
here, read Q as theta.
In horizontal direction:
Fe = T*sin(Q)
(where T is the tension in the string and Fe is the electric force between two charges)
Fe = ...
With good explanations and calculations, the problems are solved.