Chapter 15 - Electric Charge, Forces, and Fields - Learning Path Questions and Exercises - Exercises - Page 556: 9

a). $1$ b). $\frac{1}{4}$ c). $\frac{1}{2}$

We have $F=k\frac{q_{1}q_{2}}{r^{2}}$ a). one charge is doubled, the other halved, then force =$ k\frac{2q_{1}\frac{1}{2}q_{2}}{r^{2}}=F$, factor =1 b). both charges halved, then force = $k\frac{\frac{1}{2}q_{1}\frac{1}{2}q_{2}}{r^{2}}=\frac{1}{4}F$, factor = $\frac{1}{4}$ c). one charge halved, other unchanged, then force = $k\frac{\frac{1}{2}q_{1}q_{2}}{r^{2}}=\frac{1}{2}F$, factor = $\frac{1}{2}$