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BCECE Engineering BCECE Engineering Solved Paper-2011

  • question_answer
    30.      A wire has a breaking stress of\[6\times {{10}^{5}}N/{{m}^{2}}\] and          a density of \[3\times {{10}^{4}}kg/{{m}^{3}}\]. The length of the wire of the same material which will break under its town weight, (if \[g=10\,m/{{s}^{2}}\]) is

    A)  2000 m                                

    B)  2500 m

    C)  20 m                    

    D)         2 m

    Correct Answer: D

    Solution :

    Breaking stress is given by \[=6\times {{10}^{5}}\,N/{{m}^{2}}=\frac{mg}{A}\]          (But \[m=AL\rho \]) \[6\times {{10}^{5}}=\frac{Al\rho g}{A}L\rho g\] Thus,     \[L=\frac{6\times {{10}^{5}}}{\rho g}=\frac{6\times {{10}^{5}}}{3\times {{10}^{4}}\,\times 10}=2m\]


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