Question

A positive charge Q is placed at the origin. Four other positive charges are placed on a circle in the x-y plane centered on Q as shown. The top charge is located on the y axis and has a magnitude of 3q. The three bottom charges are symmetric about the y axis as shown and each has magnitude q.
1) Which of the following statements best describes FX, the x component of the net force on the charge at the origin
FX > 0
FX = 0
FX < 0

3) For the collection of charges shown in the above problem, which of the following statements best describes FY, the y component of the net force on the charge at the origin
FY > 0
FY = 0
FY < 0

Answer 1

1. FX = 0 since the bottom charges are symmetrical about the y axis and the top charge is aligned with the y-axis
3. FY > 0 since the bottom charges do not equate the top charge. The bottom charges have horizontal components which is less than q and adding them all, will not result to 3q.