Find time given velocity and distance

1. Feb 5, 2010

Calhoun295

1. The problem statement, all variables and given/known data

A certain vehicle requires a distance of 29 m to stop when it is traveling at 28 m/s.
(a) What magnitude of acceleration is produced by braking under these conditions?
(b) If a jaywalker is 27 m in front of the vehicle when the driver first applies the brakes, how much time does the pedestrian have to get out of the way?

2. Relevant equations

v=vo + at
x - xo = vot + $$\frac{1}{2}$$at2
v2 = vo2 + 2a(x - xo)

are the given equations for what we're learning.

3. The attempt at a solution

(a) 13.52m/s2
(b) is what I cannot find

2. Feb 5, 2010

Staff: Mentor

I'll rephrase the question: How long does it take the vehicle to cover 27 m?