Four charges 3 × 10−9 C at (0 m, 0 m),

−1 × 10−9 C at (−1 m, 1 m), −7 × 10−9 C at

(1 m, 3 m), and 6 × 10−9 C at (4 m, −1 m),

are arranged in the (x, y) plane.

Find the magnitude of the resulting

force on the 3 nC charge at the origin

(0 m,0 m). The Coulomb constant is

8.98755 × 109 N · C

2

/m2

.

Answer in units of N

What angle does the resultant force on the

3 × 10−9 C charge at the origin make with

the positive x axis? Quadrant I lies between

0

◦

and 90◦

, quadrant II between between 90◦

and 180◦

, etc

Three charges are arranged in the (x, y)

plane as shown.

-7 nC at (1,3)

6 nC at (4,-1)

-1 nC at (-1,1)

Find the electric potential Vo at the origin

(0,0). Let V = 0 at infinity.

Answer in units of V

I already attempted once but got the wrong answer. Could someone please enlighten me?