Physics question below?

Question

A charge of +q is located at the origin, while an identical charge is located on the x axis at x= 0.55 m. A third charge of +5 q is located on the x axis at such a place that the net electrostatic force on the charge at the origin triples, its direction remain unchanged. Where should the third charge be located?

Answer 1

Ok, here you have to remeber the electric force for point charges :

Fe = K*q1*q2 / d^2

d = distance

q1 and q2 = charges

K = electrostatic constant

Force on the charge at the origin by the second charge :

K*q*q / (0.55)^2 = Fe

If you put another charge, and the electric force triples :

3Fe = k*q*q / (0.55)^2 + k*5q*q / r^2

3K*q*q / (0.55)^2 - k*q*q / (0.55)^2 = k*5q*q / r^2

2kq^2 / 0.55^2 = k5q^2 / r^2

r^2 = 5*(0.55)^2 / 2

r = 0.87

The charge should be located at x = 0.87

Answer 2

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