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Homework Help: Finding the acceleration of a balloon

  1. Dec 2, 2009 #1
    1. An empty spherical weather balloon with a mass of 5 kg has a radius of 2.879 m when fully inflated with helium. It is supposed to carry a small load of instruments having a mass of 10 kg. Taking air and helium to have densities of 1.16 kg/m^3, respectively, what will be the acceleration of the balloon and load immediately after it is released?

    2. i have a= v^2/r and Bernoulli's equation P1+.5(pv1^2+pgy1)=P2+.5(pv2^2+pgy2)

    3. I keep trying to figure a way to manipulate Bernoulli's equation to solve for v to plug into the first equation but can't get it to work. I also tried solving for escape speed (vesc=the square root of 2GM/R). But that doesn't use the densities. I'm extremely confused at this point.
  2. jcsd
  3. Dec 2, 2009 #2


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    Do you need Bernoulli's equation?
    Isn't it simply bouyant force upward and weight down.

    Remember immediately after release it has no velocity
  4. Dec 2, 2009 #3
    no i have bernoulli's equation but i don't know how to solve for the acceleration immediately after release...
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