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Physics · SYSTEMS OF PARTICLES AND ROTATIONAL MOTION
हिन्दीGiven below are two statements: Statement I: When a girl sitting on a swivel chair stretches her arms horizontally, her moment of inertia about the axis of rotation increases, leading to a decrease in her angular speed. Statement II: In the absence of external torque, the rotational kinetic energy of the girl-chair system remains strictly conserved during the stretching and folding of arms. In the light of the above statements, choose the most appropriate answer from the options given below:
Correct answer · Option 3
Statement I is correct but Statement II is incorrect.
Explanation
Statement I is correct because \( I\omega = \text{constant} \); as \( I \) increases, \( \omega \) decreases. Statement II is incorrect because rotational kinetic energy \( K = \frac{L^2}{2I} \) changes with \( I \); folding arms involves internal muscular work which changes kinetic energy.
