Q113 / 125 · BITSAT 2017 · Physics

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 ml23)

Figure

  • Correct answer
    A
    3g2l
  • B
    23g
  • C
    3g2l2
  • D
    mgl2

Solution

The moment of inertia of the uniform rod about an axis through one end and perpendicular to its length is 

=ml23

where, m is the mass and l its length.

Torque τ=Iα acting on centre of gravity of rod is given by 

τ=mgl2

also, ml23·α=mgl2

α=3g2l

Hence, the correct answer is option: 'A'.

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