posted by Anonymous .
The speed limit in a school zone is 40 km/h. A driver traveling at this speed sees a child run into the road 23 m ahead of hs car. He applies the brakes, and the car decelerates at a uniform rate of 8.0m/s^2. if the driver's reaction time is .25s, will the car stop before hitting the child?
Using Vf = Vi + at we can calculate how long it will take the car to stop from 11.11 m/s. It will take 1.39s but the reaction time adds .25s so it the time it takes will be 1.64s to stop the car.
Now use S = Vit + (1/2)at^2 to see if the car will stop before 23m.