- #1

WeiLoong

- 35

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## Homework Statement

**IF the resultant electric field at D due to the three point charges is zero, find the magnitudes of q1 q2 in terms of q**

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https://scontent-sin1-1.xx.fbcdn.net/hphotos-xft1/v/l/t34.0-12/12498556_10205376500763571_410670163_n.jpg?oh=f586685c3d06d630fad4469546c534dc&oe=568DB0E8

## Homework Equations

Electric Field

## The Attempt at a Solution

Ex = E(q1) + E(q2)x = k q1 / AB^2 + k q2 cosθ / BD^2

Ey = E(q2)y + E(q) = k q2 sinθ / BD^2 + k q / CD^2

must be

k q2 cosθ / BD^2 = - k q1 / AB^2

k q2 sinθ / BD^2 = - k q / CD^2

then

q1 = q AB^2 / (tanθ CD^2)

AB = CD

tanθ = AB / BC

then

q1 = q BC / AB = 2 q

and

q2 = - q1 BD^2 / (cosθ AB^2)

cosθ= BC / BD

then

q2 = - q1 BD^3 / (BC AB^2) = - q (BD / AB)^3 = -11,2 q

Did i make some mistake here?