Question

The volume of a balloon is 2000 m³. It is filled with helium of density 0.18 kg m⁻³. What load can it lift? Density of air is 1.29 kg m⁻³.

Answer 1

The volume of the He gas is, V = 100 m3

When a body of density ρ, volume V is immersed completely in a fluid  of density σ then,

σ = 1.29 kg/m3  and  ρ = 0.18 kg/m3 

The observed weight of the body = W - w = Vρg - Vσg

according to question:  W<w  (ρ<σ)

Net force = W - w = Vρg - Vσg = Vg(0.18 - 1.29) = - 1087.8 N

Net force in the upward direction = 1087.8 N

It can lift a load having weight less then 1087.8 N