Sat April 14, 2012 By: Nihal Sood

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 ?

Expert Reply
Sun April 15, 2012
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 
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