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Kinematics problem help

  1. Sep 28, 2008 #1
    1. The problem statement, all variables and given/known data

    A student at a window on the second floor of a dorm sees his physics professor coming along the walkway beside the building. He drops a water balloon from 18.0 m above the ground when the prof is 1.00 m from the point directly beneath the window. If the prof is 180 cm tall and walks at a rate of 0.450 m/s, does the balloon hit his head?

    3. The attempt at a solution

    Yo = 0
    y = -18.0 m + 1.8 m = -16.2 m
    g = -9.81 m/s^2
    Vo = 0
    X = 1.00 m
    Vxo = 0.450 m/s

    Balloon Drop:

    y = yo + Vo*t - 1/2*g*t^2
    -16.2 m = 0 + 0 - 1/2(9.81 m/s^2)t^2
    t^2 = 16.2 m/4.9 m/s^2
    t^2 = 3.31 s^2
    therefore, t = sqrt3.31 s^2
    = 1.82 s

    Professor Walk:

    x = Vxo*t
    1.00 m = (0.450 m/s)t
    t = 1.00 m/(0.450 m/s)
    =2.22 s

    Therefore, the balloon drops before the professor gets there.

    Can anybody please tell me if my attempt is o.k.?
     
  2. jcsd
  3. Sep 29, 2008 #2

    Kurdt

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    Staff Emeritus
    Science Advisor
    Gold Member

    Re: Kinematics

    Looks fine to me.
     
  4. Sep 29, 2008 #3
    Re: Kinematics

    Thanks Kurdt!!
     
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