- #1

blackbrawler

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## Homework Statement

In the figure the three particles are fixed in place and have charges q1 = q2 = +e and q3 = 2e. Distance a = 6.00 µm. What is the magnitude of the net electric field at point P due to the particles?

## Homework Equations

E = k*q/r^2

## The Attempt at a Solution

I looked in the back of the book and it shows that I shouldn't be multiplying by (cos45 + sin45) but I don't understand why since Electric Field is a vector value

here is my work

q1 and q2 cancel out so i only calculate q3

F = 9*10^9 * (3.2/(6^2/2)) * 10^-13 * (cos45 + sin45)

simplifies to

F = 160 * sqrt 2 = 226.274N

The actual answer is just 160N so that means I shouldn't multiply by (cos45 + sin45) even though that is the angle.

Edit: picture should be viewable

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