Question

1. Which pair of charges experiences the weakest electrostatic force?

Answer 1

In order to compare the eletrostatic forces, let's calculate each one using the formula:

`F=k(q_1q_2)/(r^2)`

Where k = 9 * 10^9, q1 and q2 are the charges and r is the distance between them.

So we have:

`\begin{gathered} q_1=3\cdot10^(-6),q_2=5\cdot10^(-6),r=2\colon \\ F=9\cdot10^9\cdot\frac{3\cdot10^(-6)\cdot5\cdot10^{-6_{}}}{2^2} \\ F=0.03375 \\ \\ q_1=3\cdot10^(-6),q_2=3\cdot10^(-6),r=2\colon \\ F=9\cdot10^9\cdot\frac{3\cdot10^(-6)\cdot3\cdot10^{-6_{}}}{2^2} \\ F=0.02025 \\ \\ q_1=3\cdot10^(-6),q_2=3\cdot10^(-6),r=3\colon \\ F=9\cdot10^9\cdot\frac{3\cdot10^(-6)\cdot3\cdot10^{-6_{}}}{3^2^{}} \\ F=0.009 \\ \\ q_1=5\cdot10^(-6),q_2=5\cdot10^(-6),r=3\colon \\ F=9\cdot10^9\cdot\frac{5\cdot10^(-6)\cdot5\cdot10^{-6_{}}}{3^2} \\ F=0.025 \end{gathered}`

So the weakest force is the one in the third case (bottom left option): charges of -3 uC and +3 uC, and distance of 3 meters.