On October 21, 2001, Ian Ashpole of the United Kingdom achieved a record altitude of 3.35 km (11,000 ft) powered by 600 toy balloons filled with helium. Each filled balloon had a radius of about 0.45 m and an estimated mass of 0.27 kg.

Question

On October 21, 2001, Ian Ashpole of the United Kingdom achieved a record altitude of 3.35 km (11,000 ft) powered by 600 toy balloons filled with helium. Each filled balloon had a radius of about 0.45 m and an estimated mass of 0.27 kg.
(a) Estimate the total buoyant force on the 600 balloons. (Enter your answer to at least two decimal places.)

oobleck · Answer

first, figure the total mass of the balloons, and then their weight
next, figure the total volume of the balloons
next, find the density of air at the given altitude
then, the lifting force of the displaced air is volume * density (in units of weight/m^2)
subtract the weight from the lifting force to find how much weight can be lifted