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Railways NTPC (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 cycles/sec and 200 cycles/sec respectively. The lowest critical speed is:

    A) 5367 rpm                      

    B) 6000 rpm

    C) 9360 rpm                      

    D) 12,000 rpm

    Correct Answer: A

    Solution :

    \[\frac{1}{f_{n}^{2}}=\frac{1}{f_{1}^{2}}+\frac{1}{f_{2}^{2}}\] \[\frac{1}{{{100}^{2}}}+\frac{1}{{{200}^{2}}}=\frac{5}{{{200}^{2}}}\] \[f_{n}^{2}=\frac{{{200}^{2}}}{5},\] \[{{f}_{n}}=5367\,\,rpm\]


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