Re: Electrostatics problem

[Leigh Palmer <palmer@SFU.CA>]

> Leigh:  Newton's 3rd law is part of translational equilibrium in this
> case.  This alone doesn't make the angles the same.

The gravitational force is entirely vertical. The horizontal components
of the tension forces must, therefore, be equal to the horizontal
components of the electrostatic forces and oppositely directed (they
equilibrate the horizontal components of the electrostatic forces). The
strings have the same lengths, so the only way the horizontal
components of forces which must lie along the strings can be made equal
is by making the strings make equal angles with respect to the vertical.

Leigh