Chapter 12.6, Problem 23ES

(a) Suppose that at time $t=t_0$ an electron has a position vector of $\text{r}=3.5\text{i}-1.7\text{j+k,}$ and at a later time $t=t_1$ it has a position vector of $\text{r}=4.2\text{i}+\text{j}-2.4\text{k}\text{.}$ What is the displacement of the electron during the time interval from $t_0\text{to}{t}_1?$

(b) Suppose that during a certain time interval a proton has a displacement of $\Delta \text{r}=0.7\text{i}+2.9\text{j}-1.2\text{k}$ and its final position vector is known to be $\text{r}=3.6\text{k}\text{.}$ What was the initial position vector of the proton?