BCECE Medical BCECE Medical Solved Papers-2010

  • question_answer
    Two simple pendulums first [A] of bob mass \[{{M}_{1}}\] and length \[{{L}_{1}}\], second  of bob mass \[{{M}_{2}}\]and length \[{{L}_{2}}\]. \[{{M}_{1}}={{M}_{2}}\] and \[{{L}_{1}}=2{{L}_{2}}\]. If the vibrational energy of both is same. Then which of the following is correct?

    A)  Amplitude of B is greater than that of A

    B)  Amplitude of B is smaller than that of A

    C)  Amplitude will be same

    D)  None of the above

    Correct Answer: B

    Solution :

    Frequency, \[n=\frac{1}{2\pi }\sqrt{\frac{g}{l}}\] \[\Rightarrow \] \[{{n}_{2}}=\sqrt{2}\,{{n}_{1}}\] \[\Rightarrow \] \[{{n}_{2}}>{{n}_{1}}\] Energy \[E=\frac{1}{2}m{{\omega }^{2}}{{a}^{2}}=2{{\pi }^{2}}m\,{{n}^{2}}{{a}^{2}}\] \[\Rightarrow \] \[\frac{a_{1}^{2}}{a_{2}^{2}}=\frac{{{m}_{2}}n_{2}^{2}}{{{m}_{1}}n_{1}^{2}}\] (\[\because \]F is same) Given \[{{n}_{2}}>{{n}_{1}}\] and \[{{m}_{1}}={{m}_{2}}\] \[\Rightarrow \] \[{{a}_{1}}>{{a}_{2}}\]


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