Answer:
[tex]1.6381\times 10^{-5}\ C[/tex]
Explanation:
F = Force between charge = 0.9 N
[tex]q_1[/tex] = Charge on particle = -0.55 μC
k = Coulomb constant = [tex]8.99\times 10^{9}\ Nm^2/C^2[/tex]
Electric Force is given by
[tex]F=\dfrac{kq_1q_2}{r^2}\\\Rightarrow 0.9=\dfrac{8.99\times 10^9\times -0.55q_2}{0.3^2}\\\Rightarrow q_2=\dfrac{0.9\times 0.3^2}{8.99\times 10^9\times 0.55\times 10^{-6}}\\\Rightarrow q_2=+1.6381\times 10^{-5}\ C[/tex]
As there is a force of attraction the other charge will have the opposite sign
The magnitude and sign of the charge is [tex]+1.6381\times 10^{-5}\ C[/tex]