RAJASTHAN ­ PET Rajasthan PET Solved Paper-2012

  • question_answer
    The stress for elastic limit of a material is\[3.5\times {{10}^{8}}N-{{m}^{-2}}\]. The minimum diameter of a rod made of this material which can support 500 N load without exceeding elastic limit will be

    A)  1.35 mm     

    B)  1.35 cm

    C)  \[1.35\times {{10}^{-6}}m\] 

    D)  2mm

    Correct Answer: A

    Solution :

     Here, stress\[=\frac{F}{A}=3.5\times {{10}^{8}}\] \[\therefore \] \[A=\frac{F}{3.5\times {{10}^{8}}}=\frac{500}{3.5\times {{10}^{8}}}\] \[=1.43\times {{10}^{-6}}{{m}^{2}}\] or   \[\pi {{r}^{2}}=1.43\times {{10}^{-6}}\] \[\Rightarrow \] \[\frac{\pi {{D}^{2}}}{4}=1.43\times {{10}^{-6}}\] \[\Rightarrow \] \[{{D}^{2}}=\frac{4\times 1.43\times {{10}^{-6}}}{\pi }=\frac{5.72\times {{10}^{-6}}}{3.14}\] or     \[D=1.35\times {{10}^{-3}}m=1.35\,mm\]


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