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Railways NTPC (Technical Ability) Theory of Machines and Machine Design Question Bank Theory of Machines

  • question_answer
    A rotor which is balanced statically but not dynamically is supported on two ball bearings L apart and at high speed of the rotor, reaction of the left bearing is R. The right side of the bearing is shifted to a new position 2L apart from the left bearing: At the same rotor speed, dynamic reaction on the left bearing in the new arrangement will:

    A) Remain same as before

    B) Become equal to 2R

    C) Become equal to \[\frac{1}{2}R\]

    D) Become equal to \[\frac{1}{4}R\]

    Correct Answer: A

    Solution :

    \[{{R}_{1}}=\frac{W}{2},\] \[W=2{{R}_{1}}\] \[{{R}_{2}}\times 2L=2{{R}_{1}}\times L\] \[{{R}_{2}}={{R}_{1}}\]


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