The reaction time for an automobile driver is 0.7 seconds. If the automobile can be deaccelerated at 5 metre per second square, calculate the total distance travelled in coming to stop from an initial velocity of 8.33 metre per second after a signal is observed.

Think of this in two parts:

1) During the initial 0.7 seconds reaction time how far does the car travel? It's initial velocity is 8.33 m/s:


d_1 = v_i t


2) As the car deccelerates, how far does it go? Use:


v_f^2 - v_i^2 = 2 a d_2


Here you know v_f = 0 , v_i = 8.33 m/s, and a = -5m/s^2 . Solve for d_2 .

Then add d_1 and d_2 together to get the total distance.