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As shown in the figure, a  bob of mass m  is tied by a  massless string whose other end portion is wound on a fly wheel (disc) of radius r  and mass  m . When released from rest the bob starts falling vertically. When it has covered a distance of h  , the angular speed of the wheel will be

Option 1 -

r 3 4 g h

Option 2 -

1 r 2 g h 3

Option 3 -

r 3 2 g h

Option 4 -

1 r 4 g h 3

0 2 Views | Posted a month ago
Asked by Shiksha User

  • 1 Answer

  • V

    Answered by

    Vishal Baghel | Contributor-Level 10

    a month ago
    Correct Option - 4


    Detailed Solution:

    m g h = 1 2 m v 2 + 1 2 l ω 2

    v = ω R (no slipping)

    m g h = 1 2 m ω 2 R 2 + 1 2 m R 2 ω 2

    m g h = 3 4 m ω 2 R 2

    ω = 4 g h 3 R 2 = 1 R 4 g h 3

     

     

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