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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