Three identical point charges in an equilateral triangle.?

Q = +3uC

What are the magnitude and direction of the net electric force on the charge in the lower left side. The side of the triangle is 0.1 m.

oldschool2014-03-11T12:43:23Z

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First determine the directions of the fields at the lower left vertex:
The field due to the top charge is at 240°
The field due to the charge at the lower right is at 180°
The magnitudes of the fields are the same E = kQ/r² = 2,696,266N/C
Sum the horizontal components:
Ex = Ecos240 + Ecos180 = -4,044,398 N/C
Sum the vertical components:
Ey = Esin240 + Esin180 = -2,335,034 N/C
Magnitude = √Ex²+Ey²) = 4,670,069 N/C at arctan(-2,335,034/-4,044,398) = 210°
F = qE = 14N at 210°