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

  • question_answer
    Two masses m1 and m2 are suspended together by a massless spring of constant K. When the masses are in equilibrium, m1 is removed without disturbing the system. The amplitude of oscillations is                     [J & K CET 2005]

    A)            \[\frac{{{m}_{1}}g}{K}\]

    B)            \[\frac{{{m}_{2}}g}{K}\]

    C)            \[\frac{({{m}_{1}}+{{m}_{2}})g}{K}\]

    D)            \[\frac{({{m}_{1}}-{{m}_{2}})g}{K}\]

    Correct Answer: A

    Solution :

                       With mass \[{{m}_{2}}\] alone, the extension of the spring l is given as \[{{m}_{2}}g=kl\]               ...(i)                    With mass \[({{m}_{1}}+{{m}_{2}})\], the extension \[{l}'\] is given by                    \[({{m}_{1}}+{{m}_{2}})g=k(l+\Delta l)\]          ....(ii)                    The increase in extension is \[\Delta l\] which is the amplitude of vibration. Subtracting (i) from (ii), we get            \[{{m}_{1}}g=k\Delta l\] or \[\Delta l=\frac{{{m}_{1}}g}{k}\]


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