Answer:
[tex]9.465534174\times 10^{-10}\ C[/tex]
Explanation:
m = Mass of balloon = 1.9 g
k = Coulomb constant = [tex]8.99\times 10^{9}\ Nm^2/C^2[/tex]
g = Acceleration due to gravity = 9.81 m/s²
r = Distance = 0.55 mm
[tex]\mu[/tex] = Coefficient of friction = 0.7
q = Charge
The gravitational force will balance the electrical force
[tex]mg=\dfrac{kq^2}{r^2}\\\Rightarrow m\dfrac{g}{\mu}=\dfrac{kq^2}{r^2}\\\Rightarrow q=\sqrt{\dfrac{mgr^2}{k\mu}}\\\Rightarrow q=\sqrt{\dfrac{1.9\times 10^{-3}\times 9.81\times (0.55\times 10^{-3})^2}{8.99\times 10^9\times 0.7}}\\\Rightarrow q=9.465534174\times 10^{-10}\ C[/tex]
The charge is [tex]9.465534174\times 10^{-10}\ C[/tex]