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JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2009

  • question_answer
        The moment of inertia of the body about on axis is\[1.2\text{ }kg\text{ }{{m}^{2}}\]. Initially the body is at rest. In order to produce a rotational kinetic energy of 1500 J, an angular acceleration of 25 rads-2 must be applied about the axis for the duration of

    A)  2 s                                         

    B)  4 s

    C)  8s                                          

    D)  10s

    Correct Answer: A

    Solution :

                    Rotational kinetic energy\[=\frac{1}{2}I{{W}^{2}}=1500\] \[\Rightarrow \]               \[\frac{1}{2}I{{(\alpha t)}^{2}}=1500\] \[\Rightarrow \]               \[(1.2){{(25)}^{2}}\times {{t}^{2}}=3000\] \[\Rightarrow \]               \[1.2\times 625\times {{t}^{2}}=3000\] \[\Rightarrow \]               \[{{t}^{2}}=\frac{3000}{1.2\times 625}=4\]                 \[t=2s\]


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