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

  • question_answer
    The length of a spring is l and its force constant is k. When a weight W is suspended from it, its length increases by x. If the spring is cut into two equal parts and put in parallel and the same weight W is suspended from them, then the extension will be                                                       [MP PMT 1994]

    A)            \[2x\]                                      

    B)            \[x\]

    C)            \[\frac{x}{2}\]                      

    D)            \[\frac{x}{4}\]

    Correct Answer: D

    Solution :

                       Spring is cut into two equal halves so spring constant of each part = 2k These parts are in parallel so \[{{K}_{eq}}=2K+2K=4K\] Extension force (i.e. W) is same hence by using \[F=kx\] Þ \[4k\times {x}'=kx\] Þ \[{x}'=\frac{x}{4}\].


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