Question

A car traveling 57.8 km/h is 21.7 m from a barrier when the driver slams on the brakes. The car hits the barrier 2.22 s later. (a) What is the car's constant deceleration magnitude before impact? (b) How fast is the car traveling at impact?

Answer 1

Part a.)

The car will have a constant negative deceleration in order to avoid hitting the barrier.

Let us first convert 57.8 km/h to m/s,

57.8 km/h =16.055 m/s.

Now, we can use the following formula:

X = ut+ (1/2) at^2

So, a = 2(X-ut) /(t^2)

a = 2(21.7-16.055*2.22)/(2.22^2) = -5. 76 m/s^2

So, Deaccleration, a_d = 5.76 m/ s^2.....answer.

b) To figure out the speed of the car during impact, we can use the following equation:

V = u+at

V = 16.055+(-5.76*2.22)

V = 3.27 m/s....Answer.

Hope this helps you.

Please thumbs up.