When you see a traffic light turn red, you apply the brakes until you come to a stop. Suppose your initial speed was 11.2 m/s, and you come to rest in 34.7 m. How much time does this take? Assume constant deceleration.

Question

anonymous · Answer

when we come to rest
                          final velocity is zero

using S=ut+0.5*a*t*t
          =ut+0.5*((vf-vi)/t)*t*t           since due to constant deceleration
          =ut-0.5*t
         =0.5*ut
     34.7=0.5*11.2*t
       t=34.7/(0.5*11.2)
        =34.7/5.6
        =6.196 seconds