Two discs A and B are mounted coaxiallay on a vertical axle. The discs have moments of inertia I and 2 I respectively about the common axis. Disc A is imparted an initial angular velocity `2 omega` using the entire potential energy of a spring compressed by a distance `x_1` Disc B is imparted an angular velocity `omega` by a spring having the same spring constant and compressed by a distance `x_2` Both the discs rotate in the clockwise direction. When disc B is brought in contact with disc A, they acquire a common angular velocity in time t. The average frictional torque on one disc by the other during this period isA. `(2Iomega)/(3t)`B. `(9Iomega)/(2t)`C. `(9Iomega)/(4t)`D. `(3Iomega)/(2t)`

Two discs A and B are mounted coaxiallay on a vertical axle. The discs

1.	Two discs A and B are mounted coaxiallay on a vertical axle. The discs have moments of inertia I and 2 I respectively about the common axis. Disc A is imparted an initial angular velocity `2 omega` using the entire potential energy of a spring compressed by a distance `x_1` Disc B is imparted an angular velocity `omega` by a spring having the same spring constant and compressed by a distance `x_2` Both the discs rotate in the clockwise direction. When disc B is brought in contact with disc A, they acquire a common angular velocity in time t. The average frictional torque on one disc by the other during this period isA. `(2Iomega)/(3t)`B. `(9Iomega)/(2t)`C. `(9Iomega)/(4t)`D. `(3Iomega)/(2t)`
Answer» Correct Answer - A Let final angular velocity be `omega_(1)`. Applying conservation of angular momentum. `(I+2I)omega_(1)=I(2omega)+2Iomega` `implies omega_(1)=(4omega)/3` now angular impulse `=` change in angular momentum `taut=2I(omega_(1)-omega)` `implies taut=2Iomega/3impliest=(2Iomega)/(3t)`

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