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A car is speeding along the motorway at 40 m s when the driver

observes an accident ahead. He slams on the brakes, the wheels lock immediately, and the car skids to a halt. You may assume that the car travels in a straight line whilst it is skidding and that the magnitude of its deceleration is 10 m s^-2.
What distance does the car travel between the time that the brakes are applied and the time that the car comes to rest, and how much time does this take?

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2 answers

  1. time to stop = t
    v = Vi - 10 t
    0 = 40 - 10 t
    t = 4 seconds to stop
    d = average speed during stop * time = 20 * 4 = 80 meters

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  2. a. V^2 = Vo^2 + 2a*d = 0,
    40^2 + (-20)d = 0,
    d = 80 m.

    b. V = Vo + a*t = 0,
    40 + (-10t = 0,
    t = 4 s.

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