JCECE Medical JCECE Medical Solved Paper-2013

  • question_answer
    If two air columns of lengths 100 cm and 101 cm sounding in their fundamental note gave 17 beats in 20 seconds, then the velocity of sound will be

    A)  277.8m/s           

    B)  300 m/s

    C)  250 m/s             

    D)  343.4 m/s

    Correct Answer: D

    Solution :

     Given, \[{{l}_{1}}=100\,cm=1\,m\] \[{{l}_{2}}=101\,cm=1.01\,m\] Number of beats per second, \[n=17/20\] Let the velocity of sound is \[v\]and \[{{v}_{1}},{{v}_{2}}\]be the fundamental frequencies of vibrations of two air columns. Then, \[{{v}_{1}}=\frac{v}{4{{l}_{1}}}=\frac{v}{4\times 1}=\frac{v}{4}\] and \[{{v}_{2}}=\frac{v}{4\times 1.01}=\frac{v}{4.04}\] As, \[{{v}_{1}}-{{v}_{2}}=n\] \[\Rightarrow \] \[\frac{v}{4}-\frac{4}{4.04}=\frac{17}{20}\] \[\Rightarrow \] \[v=343.4\,m/s\]


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