JEE Main & Advanced Sample Paper JEE Main Sample Paper-6

  • question_answer
    Directions: Question No. 27 are based on the following paragraph. When a composite wire is made by joining two wires as shown in figure In the figure given: \[{{l}_{1}}={{l}_{2}}=l,{{\mu }_{1}}=\frac{{{\mu }_{2}}}{9}=\mu .\] The tension in the strings is T. Here, \[\mu \]is the mass per unit length. What is the lowest frequency such that the junction is an antinode?

    A)  \[\frac{4}{4l}\sqrt{\frac{T}{\mu }}\]                       

    B)  \[\frac{3}{4l}\sqrt{\frac{T}{\mu }}\]

    C)  \[\frac{5}{4l}\sqrt{\frac{T}{\mu }}\]                       

    D)  \[\frac{7}{4l}\sqrt{\frac{T}{\mu }}\]

    Correct Answer: A

    Solution :

    \[{{f}_{1}}=\frac{1}{4l}\sqrt{\frac{T}{\mu }},\frac{2}{4l}\sqrt{\frac{T}{\mu }},\frac{5}{4l}\sqrt{\frac{T}{\mu }}\]etc.  (Just like closed pipe) \[{{f}_{2}}=\frac{1}{3(4l)}\sqrt{\frac{T}{\mu }},\frac{2}{3(4l)}\sqrt{\frac{T}{\mu }},\frac{5}{3(4l)}\sqrt{\frac{T}{\mu }}\]etc. or\[{{f}_{2}}=\frac{1}{12l}\sqrt{\frac{T}{\mu }},\frac{2}{4l}\sqrt{\frac{T}{\mu }},\frac{5}{12l}\sqrt{\frac{T}{\mu }}\]etc. Therefore, the lowest frequency is\[\frac{1}{4l}\sqrt{\frac{T}{\mu }}\]


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