1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Hydrostatics physics question

  1. Apr 9, 2008 #1
    1. The problem statement, all variables and given/known data
    A girl of mass 40 kg and volume of 40 liter wants to keep her head of volume 3 liter above water surface as she can't swim . how much air in Kg should she fill in her jacket??

    2. Relevant equations

    3. The attempt at a solution
    mass of girl (m) = 40 kg
    volume of girl (V) = 0.04 m^3(meter cube)
    density of girl (D) = m / V = 1000 kg/m^3
    volume of head (v') =0.003 m^3

    let the mass of air in kg be x then

    total mass of body = 40 + x
    mass of water displaced = 40 + x
    volume of water displaced = 1000(40 + x)
    volume of immersion = V - v' = .04- .003 = .397

    therefore from principle of flotation
    volume of water displaced = volume of immersion of floating body
    40000 + 1000x = .397
    x=.397-40000 = -ve value

    is my method correct??? and as " density of body = density of water " will require extra air to float.
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted