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1. The problem statement, all variables and given/known data

A particle with charge 4 µC is located on the x-axis at the point 10 cm, and a second particle with charge -3 µC is placed on the x-axis at 4 cm. What is the magnitude of the total electrostatic force on a third particle with a charge 4 µC placed on the x-axis at -2 cm? Answer in units of N.

3. The attempt at a solution

1)I converted all my variables to µC = C , and cm = m

q1 = 4 µC = 4e-6

q2 = -3 µC = -3e-6

q3 = 4 µC = 4e-6

x1 = 10 cm = 0.1 m

x2 = 4 cm = 0.04 m

x3 = -2 cm = -0.02 m

2By using Coulom's law in vector form:

F_{13}= ke(q1q3/r^{2})^r_{13}

where ^r_{13}is a unit vector directed from q1 to q3; i.e., ->r13 = ->r3 - ->r1

x13 = x3 - x1

(-0.02m)-(0.1m) = -0.12m

x23 = x3 - x2

(-0.02m)-(0.04) = -0.06 m

^x_{13}= x_{3}-x_{1}/ √(x_{3}-x_{1})^2 = -1 or -^i

^x_{23}= x_{3}-x_{2}/ √(x_{3}-x_{2})^2 = 1 or +^i

Since the forces are collinear, the force on the third particle is the algrebracis sum of the forces between the first and third and the second and third particles.

->F = ->F_{13}+ ->F_{23}

= k_{e}[q_{1}/ r^{2}_{13}X ^r_{13}+ q_{2}/ r^{2}_{23}x^r_{13}] q_{3}

After putting in the variables, I got 33.9444444445 N as my answer, but waswrong.What did i do wrong?

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# Homework Help: Electric problem

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