You testify as an “expert witness” in a case involving an accident in which car A slid into the rear of car B,

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Question by Galaxy D: You testify as an “expert witness” in a case involving an accident in which car A slid into the rear of car B,
You testify as an “expert witness” in a case involving an accident in which car A slid into the rear of car B, which was stopped at a red light along a road headed down a hill. You find that the slope of the hill is = 12.0°, that the cars were separated by distance d = 24.0 m when the driver of car A put the car into a slide (it lacked any automatic anti-brake-lock system), and that the speed of car A at the onset of braking was v0 = 18.5 m/s.

With what speed did car A hit car B if the coefficient of kinetic friction was 0.60 (dry road surface)?

Best answer:

Answer by cork
WHAT IS THE POINT?
ASK THE FLIPPING EXPERT.

What do you think? Answer below!

2 Responses to “You testify as an “expert witness” in a case involving an accident in which car A slid into the rear of car B,”

  1. warmspirited Says:

    My, my…I love these trick questions.

    Yes…some may try to answer, but if you consider that car A was a heavily laden SUV, and car B was a tiny sports car, the answer would be much different than if the roles were reversed.

    Thus the answer can only be expressed in terms of two unknown masses.

  2. Steve Says:

    Clearly, there’s no difference caused by the relative sizes of the vehicles………

    A little force diagram will quickly reveal that the normal force of car A on the roadway is m*g*cos12, so the frictional force will be
    ff = mu *m*g*cos12 and the deceleration (a = ff/m) is
    a = mu *g *cos12 Now since a and distance are known,

    delta v = sqrt(2ax) = sqrt(2*mu*g*cos12*24) = 16 615 m/s

    Subtract from the inital velocity and the answer is 1.885 m/s

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