Question

Suppose a car is traveling at +25.0 m/s, and the driver sees a traffic light turn red. After 0.340 s has elapsed (the reaction time), the driver applies the brakes, and the car decelerates at 7.00 m/s2.

Answer 1

First, we will get the distance traveled before the driver applied the brakes.
distance = velocity * time
distance = 25*0.34 = 8.5 m

Now, we will calculated the distance that the car traveled after the driver applied the brakes. To do this, we will use the equation of motion:
vf^2 = vi^2 + 2*a*d where:
vf = zero, vi = 25 m/s and a = -7 m/s^2
Note: The negative sign is only to show deceleration 
d =  1/2*(625) /(7) = 44.6428 m

The total stopping distance = 8.5 + 44.6428 = 53.1428 m