Science

Assume you are speeding down the freeway at 75 mph. The car weighs 1500 kg and the effective force of the brakes is 14400 N. The car in front of you suddenly slows down, it takes 3 seconds for the car to do so. Your initial velocity was 33.53 and your final velocity is 0. If your reaction time is 1.6 seconds, how long would it take to slow down? In meters and seconds.

asked by Athena
  1. F = ma, so a = -144/15 = -9.6 m/s^2
    75 mi/hr = 33.53 m/s

    v = Vo + at = 33.53 - 9.6t
    v=0 at t=3.49

    So, it will take 1.6 + 3.49 = 5.09 seconds to stop

    No deceleration occurs during the first 1.6 seconds, so the distance is

    s = 33.53*5.09 - 4.9*3.49^2 = 110.99 m

    posted by Steve

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