Determine the stopping distances for an automobile with an initial speed of 95 km/h and human reaction time of 1.0 s : (a) for an acceleration a = -5.5 m/s2 : (b) for a = -6.6 m/s2

(a) 89.8 m

First of all, let's convert the initial speed from km/h into m/s:

During the reaction time of , the car still travels at constant speed, so it covers a distance of

Later, it slows down with acceleration

The distance covered in this second part can be found with the following equation:

where v=0 is the final speed of the car. Solving for S2,

So the total stopping distance is

(b) 79.2 m

This exercise is identical to the first part, except that this time the acceleration is

So, the distance covered while decelerating is

So the total stopping distance is

more than, less

less than, more

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