1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Fluids mechanics Helium balloon

  1. Oct 21, 2006 #1
    A spherical helium balloon is 2.5 m in diameter and has a total mass of 6.7 kg.
    When released into the U. S. Standard Atmosphere, at what altitude will it settle?

    My first thought was that diagram has the weight of the balloon acting downward, buoyant force upwards.

    -weight + Fb = 0

    Fb = bouyant force

    -mg + (specific weight of air)(h2-h1)A =0

    My initial equation was this:

    -mg - PA(pressure) + Fb = 0 but i believe this one is wrong.

    The answer is 4000 m
  2. jcsd
  3. Oct 21, 2006 #2
    alright i think i have to solve for the altitude using the Hydrostatic pressure in gases formula.

    P = Pa ( 1- B*z/T0)^(g/R&B)

    Pa= atm pressure
    B= lapse rate 0.00650 K/m
    R = 287 (m^2)/(s^2*K)
    T0 = 288.16K
    z = altitude
    Only problem is that i need to find the pressure at that to find the altitude z.
  4. Oct 22, 2006 #3


    User Avatar
    Science Advisor

  5. Oct 22, 2006 #4
    what a weird problem to assign especially for a section on bouyancy. I calculated the density of the balloon and looked it up on the table in my book and got 4000m.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Fluids mechanics Helium balloon
  1. Helium balloon (Replies: 1)

  2. Fluid Mechanics (Replies: 2)

  3. Fluid mechanics (Replies: 2)