# Physics Midterm Help

## Homework Statement

A two point charges (Qa and Qb) are placed along the y and x axis, as shown below:

The Qa charge is placed 3 meters up from the y axis, which contains a -5.00 microcolumb charge. The Qb charge is placed 4 meters away from the x axis, which contains a 8.00 microcolumb charge.

a. Calculate the net electric Field at the origin.

## Homework Equations

E-Field on Qa = kq/r^2
E-Field on Qb = kq/r^2

[c]3. Attempt of a solution[/b]

E-Field on Qa = kq/r^2 = (9.0 E9 N m^2/C^2)(-5.00 E-6 C)/(3m)^2 = -5000 N/m
E-Field on Qb = kq/r^2 = (9.0 E9 N m^2C^2)(8.00 E-6 C)/(4m)^2 = 4500 N/m

Where do I go from here? Do I add the E-Fields or Find the Pythagorean Theorem to find the magnitude of the E-Field?

Thanks.

BTW...Dont worry Im not cheating...IM just asking a question that was asked on the midterm...that I didnt get the answer from.

## Answers and Replies

LowlyPion
Homework Helper
The E-field is a vector field.

So accounting for the contribution from the 2 charges means adding the vector components.

Looks like Pythagoras would be the way to go to calculate |E|.