CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2007

  • question_answer
    In damped oscillations, the amplitude of oscillations is reduced to one-third of its initial value\[{{a}_{0}}\]at the end of 100 oscillations. When the oscillator completes 200 oscillations, its amplitude must be

    A)  \[\frac{{{a}_{0}}}{2}\]                   

    B)         \[\frac{{{a}_{0}}}{6}\]                   

    C)  \[\frac{{{a}_{0}}}{12}\]                

    D)         \[\frac{{{a}_{0}}}{4}\]

    E)  \[\frac{{{a}_{0}}}{9}\]

    Correct Answer: E

    Solution :

    In damped oscillation, amplitude goes on decaying exponentially \[a={{a}_{0}}{{e}^{-bt}}\] where\[b=\]damping coefficient. Initially,   \[\frac{{{a}_{0}}}{3}={{a}_{0}}{{e}^{-b\times 100T}}\] where T is time of one oscillation. Or           \[\frac{1}{3}={{e}^{-100bT}}\]                    ?.. (i) Finally,        \[a={{a}_{0}}{{e}^{-b\times 200T}}\] Or           \[a={{a}_{0}}{{[{{e}^{-100bT}}]}^{2}}\]   Or           \[a={{a}_{0}}\times {{\left[ \frac{1}{3} \right]}^{2}}\]                      [from Eq.(i)] Or           \[a=\frac{{{a}_{0}}}{9}\]


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