Question

A balloon of volume 800 cm3 is filled with hydrogen gas of
density 9 x 10-5 g/ cm3 .If the empty balloon weighs 0.3 gf and
density of air is 1.3 x 10-3 g/ cm3 . Calculate the lifting power of the balloon

Answer 1

here,

the lifting power of balloon = mass of air displaced - (mass of the helium gas + balloon)

mass of helium gas = volume of gas x density = 800 x 10^-6 m³ x 0.09 kg/m³

so

mass of helium gas = 7.2 x 10^-5 kg

and mass of balloon = 0.3 gf = 0.0029 kg

and the mass of a m³ of air will be = 1 m³ x 1.3 kg/m³

or

mass of displaced air = 1.3 kg/m³

thus,

lifting power of balloon = 1.3 - (0.0029 kg + 7.2 x 10^-5) ~ 1.3 kg