RAJASTHAN ­ PET Rajasthan PET Solved Paper-2002

  • question_answer
    If the mass and radius of planet are twice the earth, then time period of second pendulum on planet will be                         

    A)  1 s

    B)  2 s            

    C)  \[2\sqrt{2\,s}\]           

    D)  \[\frac{1}{2\sqrt{2}}s\]

    Correct Answer: C

    Solution :

     \[T=2\pi \sqrt{\frac{l}{g}}=2\pi \sqrt{\frac{l}{GM/{{R}^{2}}}}=2\pi \sqrt{\frac{I{{R}^{2}}}{GM}}\] \[T\propto \frac{R}{\sqrt{M}}\] \[\frac{T'}{T}=\frac{R'}{R}\sqrt{\frac{M}{M'}}\] \[=2.\frac{1}{\sqrt{2}}=\sqrt{2}\] \[T'=\sqrt{2}T=2\sqrt{2}s\]


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