Q. A uniform rod of length l and mass m is free to rotate in a vertical plane about A. The rod initially in horizontal position is released. The initial angular acceleration of the rod is : (Moment of inertia of rod about A is ml²/3)

A) 3g/2l
B) 2l/3g
C) 3g/2l²
D) mg(l/2)
Explanation

[Solution from source] The weight acts at the centre, l/2 from A, giving torque τ = mgl/2. With I = ml²/3, α = τ/I = (mgl/2)/(ml²/3) = 3g/(2l). The expression mg(l/2) is the torque itself, not the angular acceleration. Answer (1).

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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