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JEE Main & Advanced Sample Paper JEE Main Sample Paper-28

  • question_answer
    The time period of a pendulum is 4 sec. When it is placed in a lift accelerating up with 3g then its time period will be:

    A)  \[4\sec \]                                           

    B)  \[2\sec \]

    C)  \[3\sec \]                                           

    D)  \[1\sec \]

    Correct Answer: B

    Solution :

    \[T=2\pi \sqrt{\frac{\ell }{{{g}_{e}}}}\]                 Where \[{{g}_{e}}=\frac{Tension\,\,equilibrium}{m}\] \[=\frac{mg+ma(pseudo)}{m}=g+3g=4g\] \[T=2\pi \sqrt{\frac{\ell }{4g}}=\frac{1}{2}\left( 2\pi \sqrt{\frac{\ell }{g}} \right)=\frac{1}{2}\times 4=2\sec \]


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