RAJASTHAN ­ PET Rajasthan PET Solved Paper-2011

  • question_answer
    A small object placed on a rotating horizontal turn-table just slips when it is placed at a distance of 4 cm from the axis of rotation. If the angular velocity of the turn-table is doubled the object slips when its distance from the axis of rotation is

    A)  1 cm            

    B)  2 cm

    C)  4 cm            

    D)  8 cm

    Correct Answer: A

    Solution :

     The object will slip if centripetal force \[\le \]force of friction i.e., \[\frac{m{{v}^{2}}}{r}\ge \mu R\] \[m{{\omega }^{2}}r\ge \mu mg\] \[(\because v=r\omega ,R=mg)\] \[{{\omega }^{2}}r\ge \mu g\] \[r\propto \frac{1}{{{\omega }^{2}}}\] \[\frac{{{r}_{2}}}{{{r}_{1}}}={{\left( \frac{{{\omega }_{1}}}{{{\omega }_{2}}} \right)}^{2}}\] Put \[{{r}_{1}}=4\,cm,{{\omega }_{2}},{{\omega }_{2}}=2\omega \]


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