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**1. Homework Statement**

Three balls, with charges of +4q, -2q, -q, are equally spaced along a line. The spacing between the balls is r. We can arrange the balls in three different ways: (1) +4q, -2q, -q; (2) -2q, +4q, -q; (3) +4q, -q, -2q.

(a) Which ball experiences the largest magnitude net force in each of the three cases?

(b) Express your answers below in terms of k, Q, and r. Calculate the magnitude and direction of the force applied to the ball that has the -q charge in each of the three cases.

(c) In which case does the ball of charge +4q experience the largest force?

**2. Homework Equations**

k=9x10^9

magnitude of the force between charges: F=k(q1)(q2)/(r)^2 and F=qE

magnitude of the electric field: E=kq/r^2

**3. The Attempt at a Solution**

(a) Case 1: The -2q charge has the largest force because the -q charge experiences a large force to the right and a small to the left, the -2q charge experiences a large force to the right and a large force to the right, and the +4q charge has a large force to the right and a small force to the right.

Case 2: The -q charge and the -2q charge have equal magnitude but opposite direction net forces.

Case 3: The -q charge has the largest force because the -2q charge has a large force to the left and a small force to the right and the +4q has a large force to the left and a small force to the left.

I'm just learning how to do this so I'm not sure if these are correct. Please let me know so I can move on to part (b). Thanks!