Magnitude of the Electric Force on q

[wkn0524]

1. If a = 3.0 mm, b = 4.0 mm, Q1 = -60 nC, Q2 = 80 nC, and q = 30 nC in the Figure Q1,
what is the magnitude of the electric force on q?
2. F = kq1q2/r^2 Coulomb’s Law
3. Answer is F=1.0N

I'm a beginner in electrical study, i stuck on the net force.

My steps are:
F1=kQ1Q2/a^2 , F2= kQ2q/r^2

 

[mfb]

F1 is the force between Q1 and Q2, this is not relevant here. Can you calculate the force between Q1 and q? Did you calculate F2? As both forces on q point in the same direction, just add them.

 

[wkn0524]

F1 is the force between Q1 and Q2, this is not relevant here. Can you calculate the force between Q1 and q? Did you calculate F2? As both forces on q point in the same direction, just add them.

Sure, I'm trying out more than 1 hour. Trying again.