Question

A speeding car passes a highway patrol checkpoint and then accelerates at a constant rate. 3.15 s later, the car is 240 m from the checkpoint and its speed is then 33.7 m/s. What is the acceleration of the car?

Answer 1

[s = 240 m ][V1 - speed at the checkpoint ][V2 = 33.7 m/s][a - acceleration][t = 3.15 s]s = V1*t + (at^2)/2      (1)V2 = V1 + at   =>   V1 = V2 - at      (2)(2) -> (1) :s = (V2-at)t + (at^2)/2 = V2*t - at^2 + (at^2)/2 = V2*t - (at^2)/2 (3)From (3):a = 2*(V2*t - s)/(t^2)a = -27 [ m/(s^2) ]So, V1 = 118.7 (m/s)

Answer: a = -27 [ m/(s^2) ]