# A disc of moment of inertia  is rotating with angular velocity  about an axis perpendicular to its plane and passing through its centre. If another disc of moment of inertia  about the same axis is gently placed over it, then the new angular velocity of the combined disc will be Option 1) Option 2) Option 3) Option 4)

As we discussed in

Law of conservation of angular moment -

- wherein

If net torque is zero

i.e.

angular momentum is conserved only when external torque is zero .

Li = L

Option 1)

incorrect

Option 2)

correct

Option 3)

incorrect

Option 4)

incorrect

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