The \"reaction time\" of the average automobile driver is about 0.7 s . (The rea

Question

The "reaction time" of the average automobile driver is about 0.7 s . (The reaction time is the interval between the perception of a signal to stop and the application of the brakes.) An automobile can slow down with an acceleration of 13.0 ft/s^2

A. Compute the total distance covered in coming to a stop after a signal is observed from an initial velocity of 17.0 mi/h . (in a school zone)

B. Compute the total distance covered in coming to a stop after a signal is observed from an initial velocity of 50.4 mi/h .

Explanation / Answer

1 miles/ hour = 1.467 ft/s

A) 17 miles/h = 17*1.467 =24.94 ft/s

using the equation of linear motion , we have

S = ut+0.5at^2

S = 24.94*0.7 + 0.5*(-13)*0.7^2

S = 14.2723 ft

B) 50.4 mi/h = 50.4*1.467 = 73.9368 ft/s

S = ut+0.5at^2

S = 73.9368*0.7 + 0.5*(-13)*0.7^2

S = 48.57 ft

the total distance covered before stopping = 48.57 ft

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