Answer
2.51 seconds
Work Step by Step
We are given an acceleration of $-5.2m/s^2$, an initial velocity of $137km/h$ and an end velocity of $90km/h$
We first convert units:
$137km/h=38.06m/s$
$90km/h=25m/s$
We plug these values into $v=v_{0}+at$ and solve for time:
$t=(25m/s-38.06m/s)/(-5.2m/s^2)=2.51s$
