Question

Two charged dust particles exert a force of 7.9 10-2 N on each other. What will be the force if they are moved so they are only one sixth as far apart?

Answer 1

Since force is based on this formula:
\[F=k\frac{ q1 q2}{ r^2 }\]
We can see that the only thing changing is the distance, everything else is constant. Now we can divide this equation by itself to get

\[\frac{ F_1 }{ F_2 }=\frac{ r_2^2 }{ r_1^2 }\]

And we know that r1 is 1, r2 is 1/6 and F1 is the original force! Solvable!