# Homework Help: Question about constant acceleration

1. May 27, 2006

### elizabethR

how would i do this problem...

You are driving to the grocery store at 20 m/s. You are 110 m from an intersection when the traffic light turns red. Assume that your reaction time is 0.50 s and that your car brakes with constant acceleration.

1)How far are you from the intersection when you begin to apply the brakes? I know this answer: 100m.
2) You know what distance, $x=+100\ m$, you have to travel to come to a halt, $v=0$, at the traffic light. You also know what velocity you start out with, $v_o=+20\ m/s$, when you apply the brakes at the beginning of the deceleration.