## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

(a) Potential Energy, $U$ actually increases as $r$ increases. (b) Speed is less than at $f$ when the electron is at $i$.
The electric potential energy due to a charge placed a distance $r$ form the center of the positive point charge is $U=\frac{1}{4\pi \epsilon_{0}}$$\frac{q_{1}q_{2}}{r}$ The potential energy varies as $\frac{1}{r}$ but because the two charges have opposite signs, hence increasing $r$ simply means $U$ decreases but $U$ actually increases. (b) Since, two opposite charges slow down as they move farther apart, hence speed decreases due to deceleration. Speed is less than at $f$ when the electron is at $i$.