Chapter 21, Problem 30P

In Fig. 21-26, particles 1 and 2 are fixed in place on an x axis, at a separation of L = 8.00 cm. Their charges are q₁ = +e and q₂ = −27e. Particle 3 with charge q₃ = +4e is to be placed on the line between particles 1 and 2, so that they produce a net electrostatic force ${\stackrel{\to }{F}}_{\text{3, net}}$ on it. (a) At what coordinate should particle 3 be placed to minimize the magnitude of that force? (b) What is that minimum magnitude?