JEE Main & Advanced Physics Kinetic Theory of Gases Question Bank Mock Test - Kinetic Theory of Gases and Laws of Thermodynamics

  • question_answer
    Certain amount of an ideal gas is contained in a closed vessel. The vessel is moving with a constant velocity\[v\]. The molecular mass of gas is\[M\]. The rise in temperature of the gas when the vessel is suddenly stopped is \[(\gamma ={{C}_{P}}/{{C}_{V}})\]

    A) \[\frac{M{{v}^{2}}(\gamma -1)}{2R(\gamma +1)}\]     

    B) \[\frac{M{{v}^{2}}(\gamma -1)}{2R}\]

    C) \[\frac{M{{v}^{2}}}{2R(\gamma +1)}\]          

    D) \[\frac{M{{v}^{2}}}{2R(\gamma -1)}\]

    Correct Answer: B

    Solution :

    [b] If m is the total mass of the gas, then its kinetic energy\[=1/2m{{v}^{2}}\]when the vessel is suddenly stopped, total kinetic energy will increase the temperature of the gas (because process will be adiabatic), i.e., \[\frac{1}{2}m{{v}^{2}}=\mu {{C}_{v}}\Delta T=\frac{m}{M}{{C}_{v}}\Delta T\] \[\Rightarrow \frac{m}{M}\frac{R}{\gamma -1}\Delta T=\frac{1}{2}m{{v}^{2}}\]           \[\left( As\,{{C}_{V}}=\frac{R}{^{\gamma -1}} \right)\] \[\Rightarrow \Delta T=\frac{M{{v}^{2}}(\gamma -1)}{2R}\]


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