Answer:
0.375
Explanation:
When the 3rd sphere touches the 1st one, the charge will then be distributed between both of them, then now the 1st sphere has only half of his original charge.
In this moment then
Sphere 1 has a charge = Q/2
Sphere 3 has a charge = Q/2
When the 3rd sphere touches the 2nd sphere again the charge is distributed in a manner that both sphere has the same charge.
How the total charge is
Q = Q/2 + Q = 3/2Q,
When the spheres are separated each one has 3/4Q
Sphere 2 has a charge = 3/4Q
Sphere 3 has a charge = 3/4Q
The electrostatic force that acts on sphere 2 due to sphere 1 is:
F = (kq1q2) / r²
F = (Q/2 * 3Q/4) / r²
F = (Q² * 3) / 8r²
From the question, F = 0.42 = kQ²/r²
Thus, we can say that
F = (0.42 * 3) / 8
F = 0.1575
Thus, the ratio between F/F =
0.1575 / 0.42
Ratio, r = 0.375
