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Homework Help: Density - voulme question

  1. Nov 29, 2007 #1
    1. The problem statement, all variables and given/known data

    A balloon is to be filled with helium (density 0.178 kg/m^3) while the air outside has density 1.29kg/m^3. the mass of the empty balloon is 80kg and it is to lift a load of 240kg
    what minimum volume is necessary for the lift off? assume that the balloon material and the load occupy negligible volumes.

    2. Relevant equations

    i am assuming that we are using P = m / V
    it gives us all the necessary units to plug into this formula but my question is how do u put the 2 densities together into the equation?

    3. The attempt at a solution

    i think i'm suppose to use the P=m/v formula but i haven't figured out how the 2 densities are to fit together. the m = 80+240 = 320kg. can anyone point me in the right direction please.
  2. jcsd
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