At the scene of an accident, there are skid marks which are 200 feet long showing where a car put on the brakes. The driver swears that he was obeying the speed limit. If we assume that the car braked with a constant deceleration of 16ft/sec^2. We can determine whether or not the driver is telling the truth. Is he? That is, how fast was he going when he applied the brakes (assume the skid marks represent the interval where the brakes were applied)? Please explain your response; note: it is not enough to give an equation and evaluate that equation for the given values. The purpose of this item is to determine where the equation comes from!

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asked by Naomi
  1. V^2 = Vo^2 = 2a*d.

    0 = Vo^2 - 32*200,
    Vo^2 = 6400, Vo = 80 Ft/s.

    Vo = 80FT/s * 1m1/5280Ft. * 3600s/h = 54.5 mi/h. = Initial velocity.

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    posted by Henry

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