physics

A car is traveling 20 m/s when the driver sees a child standing on the road. He takes 0.8 s to react, then steps on the brakes and slows at 7.0 m/s2. How far does the car go before it stops?

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  1. reaction time = 0.8 seconds at 20 m/s
    distance = 0.8 s * 20 m/s = 16 m.

    From v0²-v² = 2aS
    where v0 and v are initial and final velocities,
    a, acceleration
    S, distance travelled

    braking distance
    = (0-20²)/(2*(-7 m/s²))
    = 40.8 m.

    Total distance = ?

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  2. 40.8

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  3. 10.5

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