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JEE Advanced2012PhysicsRotational MotionActual

The general motion of a rigid body can be considered to be a combination of (i) a motion of its centre of mass about an axis, and (ii) its motion about an instantaneous axis passing through the centre of mass. These axes need not be stationary. Consider, for example, a thin uniform disc welded (rigidly fixed) horizontally at its rim to a massless, stick, as shown in the figure. When the disc-stick system is rotated a

Options

  1. AIt is vertical for both the cases (a) and (b)
  2. BIt is vertical for case (a); and is at 45^ to the x-z plane and lies in the plane of the disc for case (b).
  3. CIt is horizontal for case (a); and is at 45^ to the x - z plane and is normal to the plane of the disc for cas
  4. DIt is vertical for case (a); and is 45^ to the x-z plane and is normal to the plane of the disc for case (b).

Correct answer

A. It is vertical for both the cases (a) and (b)

Step-by-step solution

Axis of rotation is parallel to z-axis. Hence for both the cases, in stantaneous axis passing through is vertical.

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