Question

A ball rolls onto the path of your car as you drive down a quiet neighborhood street. to avoid hitting the child that runs to retrieve the ball, you apply your brakes for 1.20 s. the car slows down from 15.0 m/s to 9.00 m/s. the mass of the car is 1290 kg. (b) how far did the car move while braking?

Answer 1

Since the acceleration of car is uniform so the distance traveled by car while brakes are applied is given by

$d = \frac{v_f + v_i}{2}*t$

given that

$v_f = 9 m/s$

$v_i = 15 m/s$

$t = 1.20 s$

now plug in all data in above formula

$d = \frac{15 + 9}{2} * 1.2$

$d = 14.4 m$

so car will cover 14.4 m distance while it apply brakes