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DUMET Medical DUMET Medical Solved Paper-2004

  • question_answer
    A substance breaks down by a stress of\[{{10}^{6}}N/{{m}^{2}}\]. If the density of the material of the wire is \[3\times {{10}^{3}}kg/{{m}^{3}}\], then the length of the wire of the substance which will break under its own weight when suspended vertically, is:

    A)  66.6m         

    B)  60.0m

    C)  33,3m         

    D)  30.0m

    Correct Answer: C

    Solution :

     The internal restoring force acting per unit area of cross-section of the deformed body is called stress. If an external force F is applied to the cross-sectional area A of the body, then stress \[=\frac{F}{A}=\frac{mg}{A}\] where mass m = volume \[\times \] density =\[Al\rho \] \[\therefore \] Stress \[=\frac{Al\rho g}{A}=\rho \lg \] \[\therefore \] \[l=\frac{breaking\text{ }stress}{\rho g}\] Given, breaking stress \[={{10}^{6}}\,N/{{m}^{2}}\], \[\rho =3\times {{10}^{3}}kg/{{m}^{3}},g=10\,m/{{s}^{2}}\], \[\therefore \] \[l=\frac{{{10}^{6}}}{(3\times {{10}^{3}})\times 10}\] \[l=33.3\,m\]


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