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JEE Advanced2016PhysicsRotational MotionActual

Two thin circular discs of mass m and 4m, having radii of a and 2a, respectively, are rigidly fixed by a massless, right rod of length l = 24 a through their center. This assembly is laid on a firm and flat surface, and set rolling without slipping on the surface so that the angular speed about the axis of the rod is ω . The angular momentum of the entire assembly about the point 'O' is L → (see the figure). Which of

Options

  1. AThe magnitude of angular momentum of the assembly about its center of mass is 17 m a 2 ω 2
  2. BThe magnitude of the z - component of L → i s 55 m a 2 ω
  3. CThe magnitude of angular momentum of center of mass of the assembly about the point O is 81 m a 2 ω 2
  4. DThe center of mass of the assembly rotates about the z-axis with an angular speed of ω 5

Correct answer

A. The magnitude of angular momentum of the assembly about its center of mass is 17 m a 2 ω 2

Step-by-step solution

Magnitude of angular momentum of the assembly about its centre of mass = m a 2 2 ω + 4 m 2 a 2 2 ω = 17 m a 2 2 ω

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