Two charged particles of each of mass $3 \mathrm{~g}$ and charge $0.2 \mu \mathrm{C}$ stay in (vacuum)…
Two charged particles of each of mass $3 \mathrm{~g}$ and charge $0.2 \mu \mathrm{C}$ stay in (vacuum) equilibrium on a horizontal surface with a separation of $20 \mathrm{~cm}$. The coefficient of friction is
$\left[\frac{1}{4 \pi \epsilon_0}=9 \times 10^9 \mathrm{Nm}^2 \mathrm{C}^{-2}\right]\left(\mathrm{g}=10 \mathrm{~ms}^{-2}\right)$