Railways NTPC (Technical Ability) Engineering Mechanics and Strength of Materials Question Bank Engineering Mechanics

  • question_answer
    A tapering bar (diameters of end sections being \[{{d}_{1}}\] and\[{{d}_{2}}\]) and a bar of uniform cross-section ?d? have the same length and are subjected to the same axial pull. Both the bars will have the same extension if ?d' is equal to:

    A) \[\frac{{{d}_{2}}+{{d}_{2}}}{2}\]                  

    B) \[\sqrt{{{d}_{1}}{{d}_{2}}}\]

    C) \[\sqrt{\frac{{{d}_{1}}{{d}_{2}}}{2}}\]                       

    D) \[\sqrt{\frac{{{d}_{1}}+{{d}_{2}}}{2}}\]

    Correct Answer: B

    Solution :

    \[\frac{4Pl}{\pi E{{d}_{1}}{{d}_{2}}}=\frac{4Pl}{\pi E{{d}^{2}}}\] \[\therefore \,\,d=\sqrt{{{d}_{1}}{{d}_{2}}}\]


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