A uniform flag pole of length L and mass M is pivoted at the ground by a frictionless hinge and makes angle θ with the horizontal. Its moment of inertia about the hinge is I=ML²/3. What is the linear acceleration of the free end immediately after release?

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G1 Physics · Accepted Answer

Torque about the hinge is Mg(L/2)cosθ. Thus α=[Mg(L/2)cosθ]/(ML²/3)=3g cosθ/(2L). The free end is at radius L, so a=αL=(3/2)g cosθ. Hence option D.