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CET Karnataka Medical CET - Karnataka Medical Solved Paper-2008

  • question_answer
    A simple pendulum is suspended from the ceiling of a lift. When the lift is at rest its time period is T. With what acceleration should the lift be accelerated upwards in order to reduce its period to T/2? (\[g\]is acceleration due to gravity).

    A)  2 g           

    B)  3 g

    C)  4 g           

    D)  g

    Correct Answer: B

    Solution :

    Time period of simple pendulum is given by \[T=2\pi \sqrt{\frac{l}{g}}\] ...(i) When the lift is moving up with an acceleration a, then tune period becomes \[T=2\pi \sqrt{\frac{l}{g+a}}\] Here,         \[T=\frac{T}{2}\] \[\Rightarrow \] \[\frac{T}{2}=2\pi \sqrt{\frac{l}{g+a}}\] ?(ii) Dividing Eq. (ii) by Eq. (i), we get a = 3g


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