J & K CET Engineering J and K - CET Engineering Solved Paper-2010

  • question_answer
    Two springs of spring constants \[{{k}_{1}}\] and \[{{k}_{2}}\] are joined in series and a mass m is attached to them as shown in figure. The time-period of oscillations of the springs is

    A)  \[T=\pi \sqrt{\frac{m({{k}_{1}}+{{k}_{2}})}{{{k}_{1}}{{k}_{2}}}}\]

    B)  \[T=2\pi \sqrt{\frac{m({{k}_{1}}+{{k}_{2}})}{{{k}_{1}}{{k}_{2}}}}\]

    C)  \[T=2\pi \sqrt{\frac{m}{{{k}_{1}}+{{k}_{2}}}}\]

    D)  \[T=2\pi \sqrt{\frac{m({{k}_{1}}+{{k}_{2}})}{2{{k}_{1}}{{k}_{2}}}}\]

    Correct Answer: B

    Solution :

    In series combination spring constants of combination \[\frac{1}{{{k}_{s}}}=\frac{1}{{{k}_{1}}}+\frac{1}{{{k}_{2}}}\] \[\Rightarrow \] \[{{k}_{s}}=\frac{{{k}_{1}}{{k}_{2}}}{{{k}_{1}}+{{k}_{2}}}\] Time period of combination \[T=2\pi \sqrt{\frac{m}{{{k}_{s}}}}=2\pi \sqrt{\frac{m({{k}_{1}}+{{k}_{2}})}{{{k}_{1}}{{k}_{2}}}}\]


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