Having some difficulty with this problem - the problem listed is incorrect here

Question

Having some difficulty with this problem - the problem listed is incorrect here on the website for the book.

The "reaction time" of the average automobile driver is about 0.700 seconds. (The reaction time is the interval between the perception of a signal to stop and the application of the brakes.) If an automobile can slow down with an acceleration of 12.0 ft/s2, compute the total distance covered in coming to a stop after a signal is observed

(a) from an initial velocity of 15.0 mi/h (in a school zone)

and

(b) from an initial velocity of 55.0 mi/h.

Explanation / Answer

a. total distance = d1 + d2 d1 is distance travelled while reacting = 15*6*.7/4.1 ft = 15.37 ft d2 is stopping distance = ut- 0.5 at^2 t = u/a = 21.95/12 = 1.83 sec d2 = 0.5*1.83^2*12 = 20.09 distance = 35.46 ft b. total distance = d1 + d2 d1 is distance travelled while reacting = 55*6*.7/4.1 ft = 56.34 ft d2 is stopping distance = ut- 0.5 at^2 t = u/a = 21.95/12 = 6.71 sec d2 = 0.5*6.71^2*12 = 270.1 distance = 326.44 ft

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