Answer
Challenger.
Work Step by Step
Using Formula (10) and Formula (11) from the book:
\[
\begin{array}{l}
s(t)=v_{0} t+s_{0}+\frac{a}{2} t^{2} \\
v(t)=v_{0}+a t
\end{array}
\]
\[
0=s(t)=-100+8 t+0.25 t^{2} \Rightarrow t=9.6125 \mathrm{s}
\]
Time for theleader: $ v_{0}=8, s_{0}=-100, a=0.5$ and $s(t)=$ 0
\[
0=s(t)=-115+12 t\Rightarrow t=\frac{115}{12} \approx 9.583 \mathrm{s}
\]
Time for the challenger: $s_{0}=-115, v_{0}=12$ and $s(t)=0$
So, we note that the time of the challenger is less, and therefore the challenger wins.
