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NEET-XI-Physics

07: System of particles and Rotational Motion

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  • #12
    A solid cylinder of mass 20 kg rotates about its axis with angular speed 100 rad s-1. The radius of the cylinder is 0.25 m. What is the kinetic energy associated with the rotation of the cylinder? What is the magnitude of angular momentum of the cylinder about its axis?
    Ans : M = 20 kg

    Angular speed, w = 100 rad s-1; R = 0.25 m

    Moment of inertia of the cylinder about its axis

    =1/2 MR2 = 1/2 x 20 (0.25)2 kg m2 = 0.625 kg m2

    Rotational kinetic energy,

    Er = 1/2 Iw2 = 1/2 x 0.625 x (100)2 J = 3125 J

    Angular momentum,

    L = Iw = 0.625 x 100 Js= 62.5 Js.