Pay load is defined as the difference between the mass of displaced air and the mass of the balloon. Calculate the pay load when a balloon of radius 10 m, mass 100 kg is filled with helium at 1.66 bar at 27°C. (Density of air = 1.2 kg m3 and R = 0.083 bar dm3 K1 mol1).

Given

Radius of the balloon, r = 10 m


Volume of the balloon = 4/3 x πr3


= 4/3 x 22/7 x 103


= 4190.5 m3


Thus, the volume of the displaced air is 4190.5 m3.


Also, given that


Density of air = 1.2 kg m-3


Then, mass of displaced air = 4190.5 × 1.2 kg


= 5028.6 kg


From ideal gas equation we know that: -


PV = nRT


PV = m/M x RT


Where, P = pressure = 1.66bar


V= volume = 4190.5 m3


R = universal gas constant = 0.083 bar dm3 K–1 mol–1


T= temperature = 27 + 273 = 300K


m = mass of helium inside the balloon


M = molar mass of helium = g




=1117.5kg


Now, total mass of the balloon filled with helium:


= (100 +1117.5) kg


= 1217.5 kg


Hence, pay load = (5028.6 – 1217.5) kg = 3811.1 kg


The pay load of the balloon is 3811.1 kg.


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