# Question #54e33

##### 1 Answer

We draw a free-body diagram for one of the charged balls, say left. This is shown in the figure below.

All the forces acting on the charged ball are in equilibrium.

One force is tension

Equating the magnitude of vertical component of tension with weight of the ball we get

and equating the magnitude of horizontal component of tension with the magnitude of electrostatic force we get

where

Dividing (2) by (1) we get

It is given that the angle between the silk threads is small (

From the geometry of the figure we see that

Using (4) and (5) equation (3) reduces to

Substituting the value of Coulomb's constant