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Homework Help: Object dropped from plane - where does it land?

  1. Sep 14, 2008 #1

    x^2

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    1. The problem statement, all variables and given/known data
    A plane is dropping an object from a height of 227m, such that it lands at a group of people on the ground. The speed of the plane is 60 m/s. How many meters before the group does the plane have to drop the object such that it lands at their position?


    2. Relevant equations
    xf = xi + vix delta t + (1/2) ax(delta t)2

    3. The attempt at a solution

    From my understanding, I need to break up the x and y components of this problem. If I can find the time it takes the object to hit the ground, I can multiply it by the plane's velocity and see what distance the plane must be from the observers for the package to hit its target.

    227 m = 9.8t m/s^2
    (227 m)/(9.8 m/s^2) = t
    t^2 = 23.162
    t = sqrt(23.162)
    t = 4.813 seconds

    Now that I have the time it took for the object to fall, I can multiply it by the plane's velocity to see how far in the x direction the object will travel in 4.813 seconds:

    4.813 s * 60 m/s = 288.78 m

    This is the answer I get, but it isn't correct. I can't see how multiplying the velocity by the time is wrong, but perhaps I have the wrong time?

    Thanks,
    x^2
     
  2. jcsd
  3. Sep 14, 2008 #2

    Redbelly98

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    Staff Emeritus
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    Something is wrong with that equation, since the units are different on the 2 sides:

    m ≠ s ⋅ m/s^2
    m ≠ m/s
     
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