RAJASTHAN PMT Rajasthan - PMT Solved Paper-2002

  • question_answer
    Two simple pendulum first 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 these vibrational energy of both is same. Then which is correct?

    A)  Amplitude of B greater than A

    B)  Amplitude of B smaller than A

    C)  Amplitudes will be same

    D)  None of these

    Correct Answer: B

    Solution :

                                    \[n=\frac{1}{2\pi }\sqrt{\frac{g}{l}}\] \[n\propto \frac{1}{\sqrt{l}}\]                                                 \[\frac{{{n}_{1}}}{{{n}_{2}}}=\sqrt{\frac{{{l}_{2}}}{{{l}_{1}}}=\sqrt{\frac{{{L}_{2}}}{2{{L}_{2}}}}}\]                                                 \[\frac{{{n}_{1}}}{{{n}_{2}}}=\frac{1}{\sqrt{2}}\] \[\Rightarrow \]                               \[{{n}_{2}}=\sqrt{2}{{n}_{1}}\]                                                 \[{{n}_{2}}>{{n}_{1}}\]                 Energy                  \[E=2{{\pi }^{2}}m{{n}^{2{{a}^{2}}}}\]                 Energy is same  \[\frac{a_{1}^{2}}{a_{2}^{2}}=\frac{{{m}_{2}}n_{2}^{2}}{{{m}_{1}}n_{1}^{2}}\]                                 \[{{n}_{2}}>{{n}_{1}}\,and\,{{m}_{1}}={{m}_{2}}\]                 \[\therefore \]  \[{{a}_{1}}>{{a}_{2}}\]


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