Answer
(b) $387.2 \mathrm{ft}$
(a) $2.2 s$
Work Step by Step
Formulas for position and velocity
\[
\begin{array}{l}
v_{0}+a t =v(t) \\
v_{0} t+s_{0}+\frac{a}{2} t^{2}=s(t)
\end{array}
\]
(a) $66=v(t)=88-10 t$
$t=\frac{-22}{-10} \mathrm{s}=2.2 \mathrm{s}$
$ v_{0}=88, a=-10$ and $v(t)=45 \mathrm{mi} / \mathrm{h}=66 \mathrm{ft} / \mathrm{s}$
(b) $0=v(t)=88-10 t$
$t=8.8 \mathrm{s}$
Determine $s(t)$ at $t=8.8$ with $s_{0}=0$
$ v_{0}=88, a=-10$ and $0=v(t)$
$s(8.8)=88 \cdot 8.8-5 \cdot 8.8^{2}=387.2 \mathrm{ft}$
