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Hydrostatics physics question

  • Thread starter sovankc
  • Start date
9
0
1. Homework Statement
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. Homework 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)
then
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.
 

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