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  5. Time and Motion

9th Class Science Time and Motion Question Bank Motion

  • question_answer
    A phonograph record on turn table rotates at 30 rpm. The linear speed of a point on the record at the needle at the beginning of the recording when it is at a distance of 14 cm from the centre is

    A)  22 cm/ sec       

    B)         44 cm/sec  

    C)  48 cm/sec       

    D)         52 cm/sec

    Correct Answer: B

    Solution :

    \[\omega =2\pi n=2\pi \times \frac{30}{60}=\pi \,\,rad/\sec \]               \[v=r\omega =14\times \pi \]                 \[=14\times \frac{22}{7}=\mathbf{44}\,\,\mathbf{cm/sec}\]


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