JEE Main & Advanced Sample Paper JEE Main - Mock Test - 4

  • question_answer
    A cord is wound round the circumference of wheel of radius r. The axis of the wheel is horizontal and moment of inertia about it is I. A weight mg is attached to the end of the cord and falls from the rest. After falling through a distance h, the angular velocity of the wheel will be

    A) \[\sqrt{\frac{2gh}{I+mr}}\]        

    B) \[{{\left[ \frac{2mgh}{I+m{{r}^{2}}} \right]}^{1/2}}\]

    C) \[{{\left[ \frac{2mgh}{I+2m{{r}^{2}}} \right]}^{1/2}}\]

    D)  \[\sqrt{2gh}\]

    Correct Answer: B

    Solution :

    We know \[\text{v}=\sqrt{\frac{2gh}{1+\frac{{{k}^{2}}}{{{r}^{2}}}}}\]  \[\therefore \,\,\omega =\frac{\text{v}}{r}=\sqrt{\frac{2gh}{{{r}^{2}}+{{k}^{2}}}}\] \[\omega =\sqrt{\frac{2mgh}{m{{r}^{2}}+m{{k}^{2}}}}=\sqrt{\frac{2mgh}{m{{r}^{2}}+I}}=\sqrt{\frac{2mgh}{I+m{{r}^{2}}}}\]


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