Question

Two identically charged small spheres carrying charge q and mass m are suspended by strings of equal length. At equilibrium, if angle between the strings becomes 90, then the electrostatic force between them will be

Answer 1

Let m is the mass of each ball and balls are suspended from a common point by two strings of equal length L, at equilibrium condition angle between stings is 90°

at equilibrium ,

Tcos45 = mg

And , Tsin45= Kq²/r² ,where r = 2Lsin45

hrbce electrostatic force =Kq²/(4L²sin²45)