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    Physics
    Mechanics
    Easy

    Question

    A disc is rotating with an angular velocity omega0. A constant retarding torque is applied on it to stop the disc. The angular velocity becomes (omega0/2) after n rotations. How many more rotations will it make before coming to rest?

    1. n
    2. 2n
    3.  n/2
    4. n/3

    The correct answer is: n/3

      From third equation, omega squared equals omega subscript 0 superscript 2 minus 2 alpha theta
      not stretchy rightwards double arrow left parenthesis omega subscript 0 divided by 2 right parenthesis squared equals omega subscript 0 superscript 2 minus 2 alpha left parenthesis 2 straight n pi right parenthesis
      not stretchy rightwards double arrow 4 pi straight n alpha equals 3 divided by 4 omega subscript 0 superscript 2 horizontal ellipsis horizontal ellipsis for _ of left parenthesis 1 right parenthesis
      Let no. of rotations before coming to rest =n'
      not stretchy rightwards double arrow 0 equals left parenthesis omega subscript 0 over 2 right parenthesis squared minus 2 alpha left parenthesis 2 pi straight n to the power of straight prime right parenthesis not stretchy rightwards double arrow 4 pi straight n to the power of straight prime alpha equals fraction numerator omega subscript 0 superscript 2 over denominator 4 end fraction horizontal ellipsis. left parenthesis 2 right parenthesis
           Error converting from MathML to accessible text.
      from (1)/(2) Error converting from MathML to accessible text.

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