In an auto accident, a car hit a pedestrian and the driver then slammed on the b

Question

In an auto accident, a car hit a pedestrian and the driver then slammed on the brakes to stop the car. During the subsequent trial, the driver's lawyer claimed that the driver was obeying the posted 35.0 mph speed limit, but that the limit was too high to enable him to see and react to the pedestrian in time. You have been called as the state's expert witness. In your investigation of the accident site, you make the following measurements: The skid marks made while the brakes were applied were 325 ft long, and the tread on the tires produced a coefficient of kinetic friction of 0.300 with the road.


In your testimony in court, will you say that the driver was obeying the posted speed limit?

If the driver's speeding ticket is $10 for each mile per hour he was driving above the posted speed limit, would he have to pay a ticket, and if so, how much would it be?

Explanation / Answer

s = 330 ft, u = 0.3 deacceleration of car = ug = 3 m/sec^2 => v^2 =u^2 -2*a*s [ s = 330 ft =100.584 m, v=0] => u = 24.56 m/sec = 1.473 km /min = 88.438 km/hr=54.95 miles/hr so driver has to pay = (54.95-35)*10 = $199.5 = $ 200 approx

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