If three charges q,q and -q are placed at vertices of an equilateral triangle of side L,what is the force on each charge ?

F₁ = K q q /L² = K q² /L²

 

F₂ = K q q /L² = K q²/L²

 

These are the two forces experienced by the charge (q) by -q and q. But these forces will be opposite in direction because one will be attractive & other will be replusive force.

 

And the angle between them will be 120 degree.

 

So net force will be = F₁ Cos 60 + F₂ Cos 60 

 

F = K q²/L² Cos 60 + K q² /L² Cos 60