Question

tony stewart has a fast reaction time of 0.125s. While he is racing at a constant velocity of 185 mph he sees a crash in front of him. It takes him 0.125 s to step on the brakes after seeing the accident. Once he steps on the brakes, the car undergoes a constant acceleration of -8.45 m/s2 (1 mile= 1609m) How long does it take him to come to a complete stop? How far does he go before coming to a stop?

Answer 1

It will take him

T = 185[miles/hour]/8.45[metres/second²] = 185*1609/3600[metres/second]/8.45[metres/second²] ≈ 9.79 second

to come to a complete stop after applying the brakes.

He'll go

L = (0.125[s] + 9.79[s]/2)*185*1609/3600[m/s]/2 ≈ 207.54 metres

before coming to a stop.