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Homework Help: Free fall acceleration

  1. Sep 3, 2010 #1
    1. The problem statement, all variables and given/known data

    a hot air balloon is ascending at the rate of 10 m/s and is 61 m above the ground when a package is dropped over the side.

    with what speed does it hit the ground

    2. Relevant equations

    y(final) - y(initial)= vt + .5at^2
    v(final)=v(initial) + at

    a= -g = 9.8 m/s
    v(initial)= 10m/s
    y(initial)=61m
    y(final)=0m
    v(final)=?
    t=4.69 s and -2.65


    3. The attempt at a solution

    what i did was used the equation V(final)=V(inital) + at and plugged in the numbers

    V(final)= 10m + 9.8(4.69) = 55.962

    not sure what i am doing wrong. am i using the wrong initial velocity?
     
  2. jcsd
  3. Sep 3, 2010 #2

    ehild

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    Homework Helper

    The balloon is ascending so the initial velocity is upward, the final is downward. g is downward, the initial velocity and the acceleration have opposite signs.


    ehild
     
  4. Sep 3, 2010 #3
    I think the sign of your initial velocity is wrong.
     
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