Manipal Medical Manipal Medical Solved Paper-2008

  • question_answer
    When a rod is heated but prevented from expanding, the stress developed is independent of

    A)  material of the rod

    B)  rise in temperature

    C)  length of rod

    D)  None of the above

    Correct Answer: C

    Solution :

     \[{{L}_{t}}={{L}_{o}}(1+\alpha \Delta \theta )\] \[\Delta L={{L}_{t}}-{{L}_{0}}={{L}_{0}}\alpha \Delta \theta \] ?(i) If the same rod of length Lots subjected to stress along its length, then extension in length can be. calculated by Hookes law. \[Y=\frac{stress}{strain}=\frac{stress}{\Delta L/{{L}_{0}}}\] \[=\frac{{{L}_{0}}\times stress}{\Delta L}\] \[\therefore \] \[\Delta L=\frac{{{L}_{0}}\times stress}{Y}\] ...(ii) If the rod is prevented from expanding, we have \[{{L}_{0}}\alpha \Delta \theta =\frac{{{L}_{0}}\times stress}{Y}\] \[\therefore \]Stress \[=Y\alpha \,\Delta \theta \]      (independent, of\[{{L}_{0}}\]).


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