Railways Technical Ability Vibration Analysis Question Bank Vibration Analysis

  • question_answer Suppose two rotors with inertias \[{{l}_{1}}\] and \[{{l}_{2}}\] on shafts of Length \[{{l}_{1}}\] and \[{{l}_{2}}\] respectively, are connected by gears such that the speed of the \[{{l}_{2}}\] rotor is always G times that of the \[{{l}_{2}}\] rotor. This system may, for vibration analysis, he treated as being on one shaft (integral with \[{{i}_{1}}\]) if:

    A) \[{{l}_{1}}\] is changed to \[{{G}^{2}}{{I}_{1}}\]

    B) \[{{I}_{2}}\] is changed to \[{{G}^{2}}{{I}_{2}}\]

    C) \[{{I}_{1}}\] is changed to \[{{\text{I}}_{\text{1}}}\text{/}{{\text{G}}^{\text{2}}}\]

    D) \[{{I}_{2}}\] is changed to \[{{\text{I}}_{2}}\text{/}{{\text{G}}^{\text{2}}}\]

    Correct Answer: B

    Solution :

    \[\frac{{{n}_{2}}}{{{n}_{1}}}=G\] \[I_{2}^{'}={{G}^{2}}{{I}_{2}}\]

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