science 10

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A student driver is travelling at 22.2 m/s and sees a school zone ahead. Using her brakes, she accelerates at -2.8 m/s2 to reduce her velocity to 8.2 m/s. How much time did it take to change her velocity?

  • science 10 -

    (deceleration rate)*(time) = (speed change)

    She reduces her speed by 14 m/s, so the change is -14 m/s.

    time = (-14 m/s)/(-2.8 m/s^2)
    = 5 seconds

  • science 10 -

    u=22.2m/s
    a=-2.8m/s2
    v=8.2m/s
    t=?
    v=u+at (equation)
    8.2=22.2+(-2.8)t
    8.2-22.2=-2.8t
    -14=-2.8t ('-' sign is cancelled from both the sides)
    14/2.8=t
    5=t
    hence time taken is 5 seconds

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