JEE Main & Advanced Physics Simple Harmonic Motion Question Bank Critical Thinking

  • question_answer
    Due to some force F1 a body oscillates with period 4/5 sec and due to other force F2 oscillates with period 3/5 sec. If both forces act simultaneously, the new period will be [RPET 1997]

    A)            0.72 sec                                  

    B)            0.64 sec

    C)            0.48 sec                                  

    D)            0.36 sec

    Correct Answer: C

    Solution :

                       Under the influence of one force \[{{F}_{1}}=m\omega _{1}^{2}y\] and under the action of another force, \[{{F}_{2}}=m\omega _{2}^{2}y\].                     Under the action of both the forces \[F={{F}_{1}}+{{F}_{2}}\]                     \[\Rightarrow \] \[m{{\omega }^{2}}y=m\omega _{1}^{2}y+m{{\omega }^{2}}y\]                     \[\Rightarrow \] \[\omega _{1}^{2}+\omega _{2}^{2}\]\[\Rightarrow \] \[{{\left( \frac{2\pi }{T} \right)}^{2}}={{\left( \frac{2\pi }{{{T}_{1}}} \right)}^{2}}+{{\left( \frac{2\pi }{{{T}_{2}}} \right)}^{2}}\]                    \[\Rightarrow \] \[T=\sqrt{\frac{T_{1}^{2}T_{2}^{2}}{T_{1}^{2}+T_{2}^{2}}}\] \[=\sqrt{\frac{{{\left( \frac{4}{5} \right)}^{2}}{{\left( \frac{3}{5} \right)}^{2}}}{{{\left( \frac{4}{5} \right)}^{2}}+{{\left( \frac{3}{5} \right)}^{2}}}}=0.48\sec \]


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