4. A driver takes 3.5 s to react to a complex situation. How far does the vehicle travel before the driver initiates a physical response to the situation (i. e., putting his or her foot on the brake)

This question is incomplete, the complete question is;

A driver takes 3.5 s to react to a complex situation while driving at a speed of 60 mi/h.

How far does the vehicle travel before the driver initiates a physical response to the situation (i.e., putting his or her foot on the brake)

the distance travelled by the vehicle, before the driver initiates a physical response is 308 ft

Explanation:    

Given that;

Reaction time t = 3.5 sec

Speed S = 60 mi/h

we convert mile to foot and hour to seconds

so

Speed S = 60 mi/h =  (60×5280)/(60×60) = 316800/3600 = 88 ft/sec

Now, The distance travelled by vehicle before the driver  initiates physical response is equal to Lag distance. i.e

Lag distance = V × t

we substitute

Lag distance = 88 ft/sec  3.5 sec

Lag distance = 308 ft

Therefore, the distance travelled by the vehicle, before the driver initiates a physical response is 308 ft

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