RAJASTHAN PMT Rajasthan - PMT Solved Paper-2010

  • question_answer
    A wheel has a speed of 1200 revolutions per minute and is made to slow down at a rate of 4 radians/s2.The number of revolutions it makes before coming to rest is

    A)  143                                       

    B)  272

    C)  314                       

    D)         722

    Correct Answer: C

    Solution :

    From equation of rotational motion                 \[{{\omega }^{2}}=\omega _{0}^{2}-2\alpha \theta \] \[\Rightarrow \]               \[0=4{{\pi }^{2}}{{n}^{2}}-2\alpha \theta \]                 \[\theta =\frac{4{{\pi }^{2}}{{\left( \frac{1200}{60} \right)}^{2}}}{2\times 4}=200\,\,{{\pi }^{2}}rad\] \[\therefore \]  \[2\pi n=200{{\pi }^{2}}\] So, the number of revolution                 \[n=100\pi =314\]


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