J & K CET Engineering J and K - CET Engineering Solved Paper-2013

  • question_answer
    The Young's modulus of a rope of \[10\text{ }m\] length and having diameter of \[2\text{ }cm\]is \[200\times {{10}^{11}}\,dyne/c{{m}^{2}}\]. If the elongation produced in the rope is \[1\text{ }cm,\] the force applied on the rope is

    A)  \[6.28\times {{10}^{5}}\,\,N\]

    B)  \[6.28\times {{10}^{4}}\,\,N\]

    C)  \[6.28\times {{10}^{4}}\text{ }dyne\]   

    D)  \[6.28\times {{10}^{5}}\text{ }dyne\]

    Correct Answer: B

    Solution :

    Young's modulus of a rope \[Y=\frac{FL}{A\Delta l}\] Given,  \[L=10m,\,\,A=\pi {{r}^{2}}=\pi {{(1)}^{2}}=\pi ;\] \[Y=20\times {{10}^{11}}\,dyne/c{{m}^{2}},\,\Delta l=1cm,\] \[F=\frac{Y.A.\Delta l}{L}\] \[F=\frac{20\times {{10}^{11}}\times 1\times 1}{10\times {{10}^{2}}}\] \[F=6.28\times {{10}^{9}}dyne\] \[F=6.28\times {{10}^{4}}N\]


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