JCECE Engineering JCECE Engineering Solved Paper-2007

  • question_answer
    The speed of earth's rotation about its axis is\[\omega \]. Its speed is increased to \[x\] times to make the effective acceleration due to gravity equal to zero at the equator. Then \[x\] is

    A) \[1\]                                     

    B) \[8.5\]

    C) \[17\]                                   

    D)  \[34\]

    Correct Answer: C

    Solution :

    Earth rotates about its own axis in\[24\,\,h\]. So,          \[T=24\times 60\times 60\,\,s\] So, angular speed of earth about its own axis                 \[\omega =\frac{2\pi }{T}=\frac{2\pi }{24\times 60\times 60}rad/s\] At equator,\[g'=g-{{R}_{e}}\omega {{'}^{2}}\] or            \[0=g-{{R}_{e}}\omega {{'}^{2}}\] or         \[\omega '=\sqrt{\frac{g}{{{R}_{e}}}}=\frac{2\pi }{84.6\times 60}\] \[\therefore \]        \[\frac{\omega '}{\omega }=\frac{24\times 60\times 60}{84.6\times 60}\approx 17\] \[\Rightarrow \]       \[\omega '=17\,\,\omega \] So, value of\[x\]is\[17\].


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