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Physics

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A driver of a car going 90.0km/h suddenly sees the lights of a barrier 40.0 metres ahead. It takes the driver 0.75 seconds before she applies the brakes, and the average acceleration during braking is -10.0 m/s squared. Does the car hit the barrier?SHow all your work. (2 parts)

  • Physics -

    V = 90km/h = 90km/h / 3600s/h = 0.025km/s = 25m/s.

    d = 25m/s * 0.75s = 18.75m = Distance
    traveled before brakes are applied.

    d = 40 - 18.75 = 21.25m = max stopping
    dist.

    Vf^2 = Vo^2 + 2ad = 0,
    (25)^2 + 2(-10)d = 0,
    625 - -20d = 0,
    -20d = -625,
    d = -625 / -20 = 31.25m = Distance traveled after brakes are applied.

    The car will hit the barrier, because it was required to stop within 21.25m
    after the brakes are applied.

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