Answer
The Porsche will win the race.
Work Step by Step
The formula $x = \frac{1}{2}at^2$ can be rearranged as:
$t = \sqrt{\frac{2x}{a}}$
We now find the time for the Porsche to travel 400 m;
$t = \sqrt{\frac{2x}{a}}$
$t = \sqrt{\frac{(2)(400~m)}{3.5~m/s^2}}$
$t = 15.1~s$
We then find the time for the Honda to travel 400 m;
$t = \sqrt{\frac{2x}{a}}$
$t = \sqrt{\frac{(2)(400~m)}{3.0~m/s^2}}$
$t = 16.3~s$
Even with a 1.0 second head start for the Honda, the Porsche will win the race.
