A car traveling 56 km/h is 20.0 m from a barrier when the driver slams on the brakes. The car hits the barrier 2.13 s later.
What is the car's deceleration before impact in m/s^2?
Jim
Assuming car decelerates at a constant rate = a , or if not, that the average deceleration is = a, then:
car changes its speed from 15.6 m/s (56 km/h) to 0 in 2.13 s which is an a = 15.6/2.13 = 7.30 m/s² ANS
Steve
Jim's answer is correct only if the car stops just as it comes to the barrier. Since no impact velocity is given, that's as far as this problem can be analyzed.