JEE Main & Advanced Sample Paper JEE Main - Mock Test - 3

  • question_answer
    A body of mass M, executes vertical SHM with periods \[{{t}_{1}}\] and \[{{t}_{2}},\] when separately attached to spring A and spring B respectively. The period of    SHM, when the body executes SHM, as shown in the figure is to. Then         

    A) \[{{t}_{0}}^{-1}={{t}_{1}}^{-1}+{{t}_{2}}^{-1}\]

    B) \[{{t}_{0}}={{t}_{1}}+{{t}_{2}}\]

    C) \[{{t}_{0}}^{2}={{t}_{1}}^{2}+{{t}_{2}}^{2}\]   

    D) \[{{t}_{0}}^{-2}={{t}_{1}}^{-2}+{{t}_{2}}^{-2}\]

    Correct Answer: D

    Solution :

    \[t=2\pi \sqrt{\frac{m}{K}}\,\,\,\,\,\,\,\,\,\,\,\Rightarrow \,\,\,\,\,\,\,K=Const.\,{{t}^{-2}}\] Here the springs are joined in parallel. So \[{{K}_{0}}={{K}_{1}}+{{K}_{2}}\]where \[{{K}_{0}}\] is resultant force constant \[\therefore \,\,\,Const.\,t_{0}^{-2}=Const.t_{1}^{-2}+Const.t_{2}^{-2}\] or,  \[t_{0}^{-2}=t_{1}^{-2}+t_{2}^{-2}\]


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