CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2007

  • question_answer
    The ratio of the velocity of sound in hydrogen\[\left( \gamma =7/5 \right)\]to that in helium \[\left( \gamma =\frac{5}{3} \right)\] at the same temperature is

    A)  \[\sqrt{\frac{5}{42}}\]                  

    B)  \[\sqrt{\frac{5}{21}}\]

    C)  \[\frac{\sqrt{42}}{5}\]                  

    D)  \[\frac{\sqrt{21}}{5}\]

    Correct Answer: C

    Solution :

    Velocity of sound in a gas                 \[v=\sqrt{\frac{\gamma \,p}{d}}\] \[\therefore \]  \[\frac{{{v}_{{{H}_{2}}}}}{{{v}_{He}}}=\sqrt{\frac{{{\gamma }_{{{H}_{2}}}}\times {{d}_{He}}}{{{d}_{He}}\times {{\gamma }_{He}}}}\]                 \[\frac{{{H}_{2}}}{He}=\sqrt{\frac{7\times 3\times 2}{5\times 5}}\] As           \[\frac{{{d}_{He}}}{{{d}_{{{H}_{2}}}}}=2\] \[\therefore \]  \[\frac{{{v}_{{{H}_{2}}}}}{{{v}_{He}}}=\frac{\sqrt{42}}{5}\]


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