NEET Physics Rotational Motion NEET PYQ-Rotational Motion

  • question_answer
    A solid cylinder of mass 2 kg and radius 4 cm is rotating about its axis at the rate of 3 rpm. The torque required to stop after \[2\pi \] revolutions is- [NEET 2019]

    A) \[12\times {{10}^{4}}\text{ }Nm\]

    B) \[2\times {{10}^{6}}\text{ }Nm\]

    C) \[2\times {{10}^{6}}\text{ }Nm\]

    D) \[2\times {{10}^{3}}\text{ }Nm\]

    Correct Answer: C

    Solution :

    [c] \[\omega _{2}^{2}=\omega _{1}^{2}+2\alpha \theta \]
    \[0={{\left( 2\pi \frac{3}{60} \right)}^{2}}-2\times 2\pi (2\pi )\alpha \]
    \[\alpha =\frac{9}{60\times 60\times 2}=\frac{1}{800}\]
    \[\tau =I\alpha =\frac{m{{r}^{2}}}{2}\alpha \]
    \[\frac{2\times 16\times {{10}^{4}}}{2}\times \frac{1}{800}=2\times {{10}^{-6}}\]


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