Mastering physics: The Electric Field at a Point Due to Two Point Charges

[silver421]

Homework Statement

A point charge q1:-4.00 nC is at the point x=0.600 meters, y=0.800 meters, and a second point charge q2:+6.00 nC is at the point x=600 meters, y=0 .

a) Calculate the magnitude of the net electric field at the origin due to these two point charges.
Express your answer in Newtons per coulomb to three significant figures.

b) What is the direction, relative to the negative x axis, of the net electric field at the origin due to these two point charges.
Express your answer in degrees to three significant figures.

$$\phi$$= _________ (up from the negative x axis)

Homework Equations

The Attempt at a Solution

I tried calculating E1 and E2 and added them both to get E but my answers are wrong

 

[CompuChip]

That is the correct way, as long as you take into account the fact that the electric field has a direction as well.

Can you show us how you calculated, for example, E1?

 

[silver421]

i used the equation E=K|q|/r^2. i used these numbers K= 8.988x10^9 q= 4.00x 10^-9 nC
r= square root of: (0.600)^2 + (0.800)^2
and i got E1= 35.95

and for the angle part i have no idea how to do it!