JEE Main & Advanced Physics Wave Mechanics Question Bank Self Evaluation Test - Oscillations

  • question_answer
    Masses \[{{M}_{A}}\] and \[{{M}_{B}}\] hanging from the ends of strings of lengths \[{{L}_{A}}\] and \[{{L}_{B}}\] are executing simple harmonic- motions. If their frequencies are \[{{f}_{A}}=2{{f}_{B}}\], then

    A) \[{{L}_{A}}=2{{L}_{B}}\,and\,{{M}_{A}}={{M}_{B}}/2\]

    B) \[{{L}_{A}}=4{{L}_{B}}\] regardless of masses

    C) \[{{L}_{A}}={{L}_{B}}/4\] regardless of masses

    D) \[{{L}_{A}}=2{{L}_{B}}\,\,\,and\,{{M}_{A}}=2{{M}_{B}}\]

    Correct Answer: C

    Solution :

    [c] \[{{f}_{A}}=\frac{1}{2\pi }\sqrt{\frac{g}{{{L}_{A}}}}\] and \[{{f}_{B}}=\frac{{{f}_{A}}}{2}=\frac{1}{2\pi }\sqrt{\frac{g}{{{L}_{B}}}}\] \[\therefore \,\,\frac{{{f}_{A}}}{{{f}_{A}}/2}=\frac{1}{2\pi }\sqrt{\frac{g}{{{L}_{A}}}}\times 2\pi \sqrt{\frac{{{L}_{B}}}{g}}\Rightarrow 2=\sqrt{\frac{{{L}_{B}}}{{{L}_{A}}}}\] \[\Rightarrow \,4=\frac{{{L}_{B}}}{{{L}_{A}}},\] regardless of mass.


You need to login to perform this action.
You will be redirected in 3 sec spinner