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 0.35 kg.
(a) Estimate the total buoyant force on the 600 balloons.
(b) Estimate the net upward force on all 600 balloons.