RAJASTHAN PMT Rajasthan - PMT Solved Paper-2010

  • question_answer
    A clock S is based on oscillation of a spring and a clock P based on pendulum motion. Both clocks run at the same rate on earth. On a planet having the same density as earth but twice the radius

    A)  S will run faster than P

    B)  P will run faster than S

    C)  they will both run at the same rate as on the earth

    D)  None of the above

    Correct Answer: B

    Solution :

    \[g=\frac{4}{3}\pi \rho GR\]. If density is same than\[g\propto R\] According to problem,\[{{R}_{p}}=2{{R}_{e}}\] \[{{g}_{p}}=2{{g}_{e}}\] For dock \[P\] (based on pendulum motion)                 \[T=2\pi \sqrt{\frac{l}{g}}\] Time period decreases on planet so it will run faster because\[{{g}_{p}}>{{g}_{e}}\]. For clock\[S\] (based on oscillation of spring)                 \[T=2\pi \sqrt{\frac{m}{k}}\] So, it does not change.


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