NEET Sample Paper NEET Sample Test Paper-59

  • question_answer
    A mono atomic gas at a pressure p, having a volume V expands isothermally to a volume 2V and then adiabatically to a volume 16V.  The final pressure of the gas is \[\left( \gamma =\frac{5}{3} \right)\]:

    A) \[64p\]                          

    B) \[32p\]

    C) \[\frac{p}{64}\]                         

    D) \[16p\]

    Correct Answer: C

    Solution :

    [c] Gas expands isothermally \[{{P}_{1}}{{V}_{1}}={{P}_{2}}{{V}_{2}}\] \[PV={{P}_{2}}(2V)\] \[P=\frac{P}{2}\] It then expands adiabatically \[{{P}_{1}}V_{1}^{\gamma }={{P}_{2}}{{V}_{2}}\] \[\frac{P}{2}{{(2V)}^{\gamma }}={{P}_{2}}{{(16V)}^{\gamma }}\] \[{{P}_{2}}=\frac{P}{2}{{\left[ \frac{2V}{16V} \right]}^{\gamma }}\] \[\gamma =\frac{5}{2}\] [monoatomic]              \[{{P}_{2}}=\frac{P}{2}{{\left[ \frac{1}{8} \right]}^{{}^{5}/{}_{3}}}\] \[=\frac{P}{2}{{\left[ \frac{1}{8} \right]}^{3\times {}^{5}/{}_{3}}}\Rightarrow \frac{P}{64}\]
    Note
    CP CV \[\gamma \]
    \[1{}^\circ \] \[\frac{5R}{2}\] \[\frac{3R}{2}\] \[\frac{5}{3}\]
    \[2{}^\circ \] \[\frac{7R}{2}\] \[\frac{5R}{2}\] \[\frac{7}{5}\]
    \[3{}^\circ \] \[\frac{9R}{2}\] \[\frac{7R}{2}\] \[\frac{9}{7}\]


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