Buoyancy problem

  • Thread starter lavster
  • Start date
  • #1
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Homework Statement


A six year old boy weights about 25 kg. Estimate the radius of a spherical helium balloon capable of lifting the boy.Solution 2.

Homework Equations



V=(4/3)*pi*r^3.

B= density of air* volume *g if in air

The Attempt at a Solution



the buoyancy must be greater than the weight.
Density of helium is 4g/22.4l = 0.180 kg/m3.
Density of air (Nitrogen) is 28g/22.4l = 1.25 kg/m3.


not sure where to go from here...

thanks
 

Answers and Replies

  • #2
217
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never mind i've got it now :)
 

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