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 air=1.2 kg m-3 and R=0.083 bar dm3 K-1 mol-1)
The payload of the ballon = mass of the displaced air – mass of the ballon
The radius of the ballon, r = 10 m, Mass of the ballon, m = 100kg
Volume of the ballon = 43πr3=43×3.14×103=4186.7m3
Now volume of the displaced air = 4186.7 m3
Given, Density of air = 1.2 kg m−3,
Therefore, the mass of the displaced air = density × volume = 4186.7×1.2= 5024.04 kg
M, Molar mass of He is 4, Temperature, T = 27+273 K = 300K
Let w be the mass of helium gas filled into the ballon.
We know that PV = n RT
here n =givenmassofsubstance(w)molecularmassofsubstance(M)
so PV=wRTM
w=PVMRT
w=1.66×4186.7×103×40.083×300
= 1116.4 Kg
The mass of filled balloon is the sum of the mass of the empty ballon and the mass of He. It is 100+1116.4=1216.4 kg.
Pay load = mass of displaced air − mass of balloon =5024.04−1216.44=3807.6 kg