Railways Technical Ability Vibration Analysis Question Bank Vibration Analysis

  • question_answer A shaft has two heavy rotors mounted on it. The transverse natural frequencies, considering each of the rotor separately, are 100 Hz and 200 Hz respectively. The lowest critical speed is:

    A) 5367 rpm                      

    B) 6000 rpm

    C) 9360 rpm                      

    D) 12000 rpm

    Correct Answer: A

    Solution :

    \[\frac{1}{\omega _{n}^{2}}=\frac{1}{\omega _{1}^{2}}+\frac{1}{\omega _{2}^{2}}\] \[\frac{1}{{{100}^{2}}}+\frac{1}{{{200}^{2}}}=\frac{1.25}{{{10}^{4}}}\] \[{{\omega }_{n}}=89.433\,\,Hz\,\,or\,\,5367\,\,rpm\]

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