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Homework Help: Helicopter and package

  1. Mar 4, 2008 #1
    1. The problem statement, all variables and given/known data
    A helicopter is ascending vertically with a speed of 5.5m/s. At a height of 100m above the Earth, a package is dropped from a window. How much time does it take the package to reach the ground?


    2. Relevant equations
    delta y = Vot + 1/2at^2


    3. The attempt at a solution
    well I know that:
    Vo= 5.5m/s
    a=-9.8 m/s^2
    delta y= -100m

    I re-wrote the equation so that I would solve it using the the quadratic formula.
    -5.5 + the square root of (5.5)^2 -4(-4.9)(100)/ 2(-4.9)
    My teacher gave us the answer of t= 5.11s, but I can't figure out how he did it.
     
  2. jcsd
  3. Mar 4, 2008 #2

    Doc Al

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    Staff: Mentor

    Here's a site with the full quadratic formula: http://mathworld.wolfram.com/QuadraticFormula.html" [Broken]. Just plug in the numbers and you'll get 2 solutions. Only one will make sense for this problem.
     
    Last edited by a moderator: May 3, 2017
  4. Mar 4, 2008 #3

    PhanthomJay

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    Science Advisor
    Homework Helper
    Gold Member

    Your equation is not quite correct it's -5.5 plus or minus the sq rt...etc. You will get 2 values for t...which is correct? (also, be sure to check all math).
     
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