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Railways NTPC (Technical Ability) Vibration Analysis Question Bank Vibration Analysis

  • question_answer
    A shaft has an attached disc at the centre of its length. The disc has its centre of gravity located at a distance of 2 mm from the axis of the shaft. When the shaft is allowed to vibrate in its natural bow-shaded mode, it has a frequency of vibration of 10 radians second. When the shaft is rotated a 300 revolutions per minute, it will whirl with a radius of:

    A) 2 mm               

    B) 225 mm

    C) 2.50 mm                      

    D) 3.00 mm

    Correct Answer: B

    Solution :

    \[\omega =\frac{2\pi \times 300}{600}=10\pi \,\text{rad/s}\] \[\beta =\frac{\omega }{{{\omega }_{n}}}\,\frac{10\pi }{10}=\pi \] \[r=\frac{e{{\beta }^{2}}}{{{\beta }^{2}}-1}=\frac{2\times {{\pi }^{2}}}{{{\pi }^{2}}-1}=225\,\,mm\]


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