(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I am a maths teacher retraining in physics, haven't recieved my text book yet but attempting the course work, I have the answer to this question and the mathematic skills to solve it, but the notes don't give any worked examples so I have no idea how to go from the law to the answer.

q. A charge q1 is located at x=1 m, y=0. What should you use for the unit vector r in Coulomb's law if you are calculating the force that q1 exerts on charge q2 located at the point x=0 y=1m

2. Relevant equations

The law I have is F_{12}=[(kq1q2)/r^2]r

3. The attempt at a solution

And I understand the question wants a vector answer and with my maths skills I drew the points and worked out that the distance from q1 to q2 is sqrt(2) and I know the answer is the vector

-sqrt(2)/2 i + sqrt(2)/2 j

Where does the negative come from and why is it over 2? I know this is a silly question but my lecture notes go from the law to this question. I assume the text book will shed more light but I was just trying to understand this part before moving on.

Thanks to anyone that has time for this :)

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# A basic Coulomb's Law question

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