Positive charge + Q is distributed uniformly along the + x-axis from x = 0 to x = a. Negative charge - Q is distributed uniformly along the -x-axis from x = 0 to x = -a.
(a) A positive point charge q lies on the positive y-axis, a distance y from the origin. Find the force (magnitude and direction) that the positive and negative charge distributions together exert on q. Show that this force is proportional to y -3 for y » a.
(b) Suppose instead that the positive point charge q lies on the positive x-axis, a distance x > a from the origin. Find the force (magnitude and direction) that the charge distribution exerts on q. Show that this force is proportional to x -3 for x » a.