physics
posted by matin .
Three charges sit on the vertices of an equilateral triangle, the side of which are 30.0 cm long. If the charges are A = +4.0 C, B = +5.0 C, and C = +6.0 C (clockwise from the top vertex), find the force on each charge.

Charge A(q1)
F12 = k•q1•q2/a².
F13 = k•q1•q3/a².
F(A) = sqrt(F12² + F13²  2•F12•F13•cos 120º).
Charge B(q2)
F21 = k•q1•q2/a².
F23 = k•q2•q3/a².
F(B) = sqrt(F21²+F23²2•F21•F23•cos120º).
Charge C (g3),
F31 = k•q1•q3/a².
F32 = k•q2•q3/a².
F(C) = sqrt(F31² + F32²  2•F31•F32•cos 120º). 
How did you get F12 and F13 ??

physics  sara, Friday, August 17, 2012 at 10:45pm
How did you get F12 and F13 ??
F12 = k•q1•q2/a²=9•10^9•4•10^6•5•10^6/0.09=2 N
F13 = k•q1•q3/a² = 9•10^9•4•10^6•6•10^6/0.09=2.4 N
F(A) = sqrt(F12² + F13²  2•F12•F13•cos 120º)=
=sqrt[4+5.762•2•2.4(0.5)] =3.82 N