- #1

shadowdn

- 1

- 0

## Homework Statement

In the figure above, charge A is -5.00 nC, charge B is 10.0 nC, and charge C is 5.00 nC. If x = 2.10 cm and y = 4.20 cm, what is the electric field at the dot?

## Homework Equations

E = kq/r^2

## The Attempt at a Solution

r = distance from A to point = sqrt(x^2+y^2)

Ea = kq/r^2 = -20'414.6 N/C

Ec = kq/x^2 = 102'040.8 N/C

Eb = kq/y^2 = 51'020.4 N/C

Eax = -20'414.6cos63.4 = -9'140.8 N/C

Eay = -20'414.6sin63.4 = -18'253.8 N/C

Enetx = Eax-Ec = -111'181.6 N/C

Enety = Eay-Eb = -69'274.2 N/C

Enet = sqrt[(-111'181.6)^2 + (-69'274.2)^2]

theta = tan^-1(Enety/Enetx) = 32 degrees

Final Answer (which was wrong): 1.13x10^5 @ 32 clockwise from horizontal

Can anyone tell me where I went wrong? Supposedly there is a special formula that I am supposed to use to find the components but I have never seen/used it before.