CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2002

  • question_answer
    The tension of a stretched string is increased by 69%. In order to keep its frequency of vibration constant, its length must be increased by:

    A) \[30%\]                               

    B) \[~20%\]

    C) \[~69%\]                             

    D) \[\sqrt{69%}\]

    Correct Answer: A

    Solution :

    \[f=\frac{1}{2l}\sqrt{T/\mu }\] \[T=\]tension \[\mu =\]mass/length \[l=\]length.    \[{{f}_{1}}=\frac{1}{2{{l}_{1}}}\sqrt{\frac{{{T}_{1}}}{\mu }}\] \[{{T}_{1}}=T+0.69\,T=1.69\,T\] \[{{l}_{1}}=?,f={{f}_{1}}\] \[\frac{1}{2l}.\sqrt{\frac{T}{\mu }}=\frac{1}{2{{l}_{1}}}\sqrt{\frac{1.69\,T}{\mu }}\] \[\frac{1}{l}=\frac{1.3}{{{l}_{1}}}\] \[{{l}_{1}}=1.3\,l\] Increase in length\[=1.3\,l-l=0.3l\]                                 \[=30%\]


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