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Homework Help: 1D - motion

  1. Sep 15, 2009 #1
    1. The problem statement, all variables and given/known data

    The height of a helicopter is given by h=3.00t^3, where h is in meters and t in seconds. After 2s, the helicopter releases a small bag. How long does it take for the bag to reach the ground?

    Xi = 0
    Xf = 24 (i got 24 meters when i plugged in seconds in h=3.00t^3)
    A(gravity) = 9.81
    Vi = 0

    2. Relevant equations

    Xf=Xi+Vi(t)+1/2at^2

    3. The attempt at a solution

    i plugged in the numbers

    24=(t)+1/2(9.81)(t^2)
    24=(t)+4.905(t^2)
    19.095=t^3

    this is where i am stuck because i dont know how to solve an equation with a letter cubed...
    i dont know if im doing this right, help?
     
  2. jcsd
  3. Sep 15, 2009 #2

    rl.bhat

    User Avatar
    Homework Helper

    Helicopter rising. Its initial velocity in the upward direction is given by dh/dt. Find vi at 2 seconds.
    Initial height from the ground xo =24 m. Final height xf = 0. Find t.
     
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