JEE Main & Advanced Physics Simple Harmonic Motion Question Bank Spring Pendulum

  • question_answer
    The force constants of two springs are \[{{K}_{1}}\] and \[{{K}_{2}}\]. Both are stretched till their elastic energies are equal. If the stretching forces are \[{{F}_{1}}\] and \[{{F}_{2}}\], then \[{{F}_{1}}:{{F}_{2}}\] is [MP PET 2002]

    A)            \[{{K}_{1}}:{{K}_{2}}\]      

    B)            \[{{K}_{2}}:{{K}_{1}}\]

    C)            \[\sqrt{{{K}_{1}}}:\sqrt{{{K}_{2}}}\]                               

    D)            \[K_{1}^{2}:K_{2}^{2}\]

    Correct Answer: C

    Solution :

                       Given elastic energies are equal i.e., \[\frac{1}{2}{{k}_{1}}x_{1}^{2}=\frac{1}{2}{{k}_{2}}x_{2}^{2}\] \[\Rightarrow \frac{{{k}_{1}}}{{{k}_{2}}}={{\left( \frac{{{x}_{2}}}{{{x}_{1}}} \right)}^{2}}\] and using \[F=kx\] \[\Rightarrow \frac{{{F}_{1}}}{{{F}_{2}}}=\frac{{{k}_{1}}{{x}_{1}}}{{{k}_{2}}{{x}_{2}}}=\frac{{{k}_{1}}}{{{k}_{2}}}\times \sqrt{\frac{{{k}_{2}}}{{{k}_{1}}}}=\sqrt{\frac{{{k}_{1}}}{{{k}_{2}}}}\]


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