Solve Buoyancy Problem: Estimate Balloon Radius for 6 Yr Old Boy

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SUMMARY

The discussion focuses on calculating the radius of a helium balloon required to lift a six-year-old boy weighing 25 kg. The buoyancy force must exceed the boy's weight, which is determined using the formula V=(4/3)*pi*r^3 for volume and the densities of helium and air. The density of helium is established as 0.180 kg/m³, while the density of air is 1.25 kg/m³. The solution involves equating the buoyancy force to the weight to find the necessary balloon radius.

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  • Understanding of buoyancy principles
  • Familiarity with the volume formula for spheres
  • Knowledge of density calculations
  • Basic grasp of gravitational force
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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
 
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