Railways Technical Ability Engineering Mechanics and Strength of Materials Question Bank Strength of Materials

  • question_answer A rectangular section beam subjected to a bending moment M varying along its length is required to develop same maximum bending stress at any cross- section. If the depth of the section is constant, then its width will vary as:

    A) \[M\]                            

    B) \[\sqrt{M}\]

    C) \[{{M}_{2}}\]                          

    D) \[\text{1/M}\]

    Correct Answer: A

    Solution :

    Bending stress, \[\sigma =\frac{M}{z}\] For \[\sigma \] to remain constant,             \[z\propto M\] For a rectangular beam of width b and depth h.             \[z=\frac{b{{h}^{2}}}{6}\] \[\therefore \]         \[b{{h}^{2}}\propto M\] For h=constant, \[b\alpha \,M\]

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