Answer
$D=155ft$
Work Step by Step
Substitute the values given in the exercise into the formula for braking distance.
First we change the miles per hour to feet per second. Multiply the mph by 1.4667 to get the ft/s.
$55*1.4667=80.67$ so $55mph=81ft/s$
$30*1.4667=44.001$ so $30mph=44ft/s$
$D=\frac{1.05(80.67^{2}-44^{2})}{64.4(0.4+0.02+\sin(-2^{\circ}))}$
$D=154.95ft$
$D\approx155ft$
