- #36
TSny
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kidi3 said:I am getting confused.. wasn't F_x i shoud have used..
Exactly, F_x is what you should use. The force that q3 exerts on q1 is
F = kq1q3/r2
The x-component of this force is Fx = Fcosθ. So,
Fx = kq1q3cosθ/r2.
q4 creates the same x-component of force on q1. So, the total force on q1 from q3 and q4 together is
2kq1q3cosθ/r2 ##\;\;\;\;## (in the positive x direction)
q2 creates a force on q1 in the negative x direction of magnitude kq1q2/R2.
So, the net force will be zero if
2kq1q3cosθ/r2 = kq1q2/R2
This leads to
2q3cosθ/r2 = q2/R2
And the error, I really don't understand how there can be a error in the equation i wrote..
Right. That's what we need to determine. So, let's go through the steps for solving the last equation above for R. I suggested what I thought was a good first step; namely, to multiply the equation through by the least common denominator r2R2. If that's not how you want to do it, that's ok. But, can you please show your next step or two in solving for R?