Estimate the number of helium balloons it would take to make Dr. Thomas float –

Question

Estimate the number of helium balloons it would take to make Dr. Thomas float – that is at least be able to slightly overcome the gravitational force on Dr. Thomas (his weight). Dr. Thomas weighs 150 lbs and there are 2.2 lbs in every 1 kg (here on Earth). Other possible helpful information is as follows: 1) the density of air is 1.29 kg/m3 and that of helium is 0.17 kg/m3 at room temperature, 2) the balloons to be used each have a mass of 1.0 g when they are empty and can expand to a maximum volume of 2.0 L.

Explanation / Answer

here,

weight of Dr. Thomas, m = 150 / 2.2 = 68.18 Kg

mass of ballon, mb = 1g = 0.001 Kg

Density of air, da = 1.29 kg/m^3
Density of helium, dh = 0.17 kg/m^3

Volume of ballon, v = 2 L = 0.002 m^3

so the Lift Foce provided by each balloon Will be
Fl = (a - h)V*g
Fl = (1.29 - 0.17)* 0.002 * 9.8
Fl = 0.022 N

Therefore, the number of balloons :
n = mg / Fl

n = (68.18*9.8) / 0.022

n = 30437.5 ballons

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