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JCECE Engineering JCECE Engineering Solved Paper-2015

  • question_answer
    A cable in the form of a spiral roll (shown in the figure) has a linear density\[\rho \]. It is uncoiled at a uniform speed\[v\]. If the total length of the cable is\[L\]. The work done in uncoiling the cable is

    A) \[\rho L{{v}^{2}}/4\]                      

    B) \[\rho L{{v}^{2}}/2\]

    C) \[\rho L{{v}^{2}}/3\]                      

    D)  \[\rho L{{v}^{2}}\]

    Correct Answer: B

    Solution :

    Initial speed of the coil is\[0\,\,m/s\]. Final speed\[=v\] (uncoiling speed) Mass of the coil\[=\rho L\] Thus, work done                 \[W=\Delta KE={{K}_{f}}-{{K}_{i}}\]                 \[=\frac{1}{2}\times (\rho L){{(v)}^{2}}-0=\frac{1}{2}\rho L{{v}^{2}}\]


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