Question

1.There are four charges, each with a magnitude of 2.5 µC. Two are positive and two are negative. The charges are fixed to the corners of a 0.29 m square, one to a corner, in such a way that the net force on any charge is directed toward the center of the square. Find the magnitude of the net electrostatic force experienced by any charge.

2.A charge of +q is located at the origin, while an identical charge is located on the x axis at x = 0.55 m. A third charge of +2 q is located on the x axis at such a place that the net electrostatic force on the charge at the origin quadruples, its direction remaining unchanged. Where should the third charge be located?

3.A charge of -3.00 µC is fixed at the center of a compass. Two additional charges are fixed on the circle of the compass (radius = 0.130 m). The charges on the circle are -4.80 µC at the position due north and +5.00 µC at the position due east. What is the magnitude and direction of the net electrostatic force acting on the charge at the center? Specify the direction relative to due east (0°).


1. Try like charges opposite each other on the corners. You can use symettry to reduce the calcs, for instance, the net force to the center...

Fnet= kqq/s^2 (2(.707) -1/(1.4^2) )

check that, I did it in my head. Notice the component of attractive forces not along the diag cancel out.

2. Try adding the charges forces on each side of the fixed charges...to the left, in between, and to the right. I think it will be in between.

3. This is simple adding for forces. I recommend do it as a vector equation, i,j coordinates.