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/s2.

Part A

Compute the total distance covered in coming to a stop after a signal is observed from an initial velocity of 15.8 mi/h . (in a school zone).

Part B

Compute the total distance covered in coming to a stop after a signal is observed from an initial velocity of 51.6 mi/h .

Explanation / Answer

a)

1 mph =1.46667 ft/s

Vi=15.8*1.46667 =23.17 ft/s

Distance travelled in t=0.7s

d1=23.17*0.7 =16.22 ft

From

Vf2=Vi2+2ad

0=23.172-2*(-13)*d2

d2=20.654 ft

Total distance

D=20.654+16.22=36.874 ft

b)

Vi=51.6*1.46667=75.68 ft/s

d1=75.68*0.7 =52.976 ft

=>0=75.682-2*13*d2

d2=220.287 ft

Total distance

D=220.287+52.976

D=273.263 ft

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