Question

An inattentive driver is traveling 15.0 m/s when he notices a red light ahead. his car is capable of decelerating at a rate of 3.35 m/s2 . part a if it takes him 0.210 s to get the brakes on and he is 66.0 m from the intersection when he sees the light, will he be able to stop in time

Answer 1

We know that v = u + at



He stops when the speed is zero; therefore



0 = 15 - 3.35 t

t = 4.48 


It takes 4.48 seconds after the driver turns on the brake for him to stop.


We know
s = ut + (1/2)at² 



s = 15*4.48 - *(1/2)(3.25)(4.48)² 

s = 33.4 meters

The distance he travels before applying the brakes is:

s = 0.21 * 15
s = 3.15 m

The total distance he travels is:
3.15 + 33.4 = 36.55 meters

He will be able to stop in time.