Manipal Medical Manipal Medical Solved Paper-2015

  • question_answer
    How many times diatomic gas should be expanded adiabatically so, as to reduce the root mean square velocity to half

    A) 16                                              

    B)  8

    C) 32                                              

    D) 64

    Correct Answer: C

    Solution :

    As, \[{{V}_{rms}}=\sqrt{\frac{3RT}{M}}=\frac{{{({{V}_{rms}})}_{1}}}{{{({{V}_{rms}})}_{2}}}=\sqrt{\frac{{{T}_{1}}}{{{T}_{2}}}}\]                 \[{{T}_{1}}V_{1}^{\gamma -1}=T_{2}^{\cdot }V_{2}^{\gamma -1}\]                   \[\frac{{{T}_{1}}}{{{T}_{2}}}={{\left( \frac{{{V}_{2}}}{{{V}_{1}}} \right)}^{\gamma -1}}\] \[\frac{{{({{V}_{rms}})}_{1}}}{{{({{V}_{rms}})}_{2}}}={{\left( \frac{{{V}_{2}}}{{{V}_{1}}} \right)}^{\frac{\gamma -1}{2}}}\] \[=\left[ \frac{{{V}_{2}}}{{{V}_{1}}} \right]\frac{\frac{7}{5}-1}{2}\] \[={{\left[ \frac{{{V}_{2}}}{{{V}_{1}}} \right]}^{\frac{2}{5}\times \frac{1}{2}}}={{\left( \frac{{{V}_{2}}}{{{V}_{1}}} \right)}^{\frac{1}{5}}}={{\left( \frac{{{V}_{1}}}{{{V}_{2}}} \right)}^{5}}\] \[{{(2)}^{5}}=32\]


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