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kspabo
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Homework Statement
In the figure particle 1 of charge q1 (at origin) and particle 2 of charge q2 = 3q1, are held at separation L on an x axis. If particle 3 of unknown charge q3 is to be located such that the net electrostatic force on it from particles 1 and 2 is zero, what must be the (a)x and (b)y coordinates of particle 3?
Homework Equations
E = k q1q2/r2
The Attempt at a Solution
We know that the third particle will be held at equilibrium between the two particles (so y = 0), so the forces on it from q1 and q2 will cancel out. From this idea we get:
E13 - E23 = 0
E13 = E23
We plug in our relevant equation:
k q1q3/r2 = k q2q3/(L-r)2
Plug in and cancel like terms:
k q1q3/r2 = k q2q3/(L-r)2
k q1q3/r2 = k 3q1q3/(L-r)2
q1/r2 = 3q1/(L-r)2
1/r2 = 2q1/(L-r)2
Attempt to isolate for r:
(L-r)/r = sqrt(2q1)And this is where I get stuck.
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