A given amount of (approximately ideal) gas is held in a spherical container. For what gas pressure the weight of the container will be minimal?
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1 Answers
Let the mass of the given ideal gas be " m " ,
the molecular mass of the given ideal gas be " M " ,
the mass density per unit volume of the container be " Ï " ,
the tensile strength of the container material be " σ " ,
the radius of the container be " r " ,
the temperature maintained inside the container be " T " .
Let us calculate the pressure exerted by the given ideal gas , which I am going to take as " P " .
P . 43 π r 3 = mM R T
Or , P = 3 m R T4 π r 3 M
For the container to sustain this pressure , we must have : -
P . π r 2 < σ . 4 π r 2
Or , P < 4 σ
Or , 3 m R T4 π r 3 M < 4 σ
Or , m R T4 σ M < 43 π r 3
Now , the weight of the container = 43 Ï€ r 3 Ï g
Hence , the minimal weight of the container , W = m Ï R T g4 σ M
Note : - I think this value of " W " is not achievable .