KVPY Sample Paper KVPY Stream-SX Model Paper-6

  • question_answer
    An ideal gas is enclosed in a cylinder at pressure of 2 atm and temperature, 300 K. The mean time between two successive collisions is \[6\times {{10}^{-8}}s.\] If the pressure is doubled and temperature is increased to 500 K, the mean time between two successive collisions will be

    A) \[2\times {{10}^{-7}}s\]                       

    B) \[4\times {{10}^{-8}}s\]

    C) \[0.5\times {{10}^{-8}}\,s\]                  

    D) \[3\times {{10}^{-6}}\,s\]

    Correct Answer: B

    Solution :

    The mean time between two collision \[\propto \frac{P}{\sqrt{T}}\]
    \[\frac{\Delta {{t}_{1}}}{\Delta {{t}_{2}}}=\frac{{{P}_{1}}}{{{P}_{2}}}\times \frac{\sqrt{{{T}_{2}}}}{\sqrt{{{T}_{1}}}}\]
    \[\Rightarrow \]   \[\frac{6\times {{10}^{-8}}}{\Delta {{t}_{2}}}=\left( \frac{\sqrt{3}}{5} \right)\times 2\]
    \[\Rightarrow \]   \[\Delta {{t}_{2}}=6\times {{10}^{-8}}\times \frac{1}{2}\sqrt{\frac{5}{3}}\]
                \[\approx 4\times {{10}^{-8}}\sec .\]


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