How Many Balloons Does It Take to Lift a Little Girl?

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A little girl holds a large number of weather balloons. How many are too dangerous, so that she starts to "fly"? Select a number of balloons and click the "up" button to find out.
Contributed by: Enrique Zeleny (May 2012)
Open content licensed under CC BY-NC-SA
Snapshots
Details
The density of air is and for helium it is
. The diameter of a weather balloon is
. The buoyancy force is equal to the weight of the displaced fluid
. The weight of the girl is
. Then around 88 balloons are needed to lift the girl.
Permanent Citation
"How Many Balloons Does It Take to Lift a Little Girl?"
http://demonstrations.wolfram.com/HowManyBalloonsDoesItTakeToLiftALittleGirl/
Wolfram Demonstrations Project
Published: May 8 2012