A pulley is hinged at the centre and a massless thread is wrapped around it. The thread is pulled with a constant force F starting from rest. If dv/dt = 0, then the angular acceleration of the ladder when α = 45° is:-

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G1 Physics · Accepted Answer

For a ladder with ends constrained on perpendicular walls, x²+y²=L². Differentiating twice and using dv/dt=0 at α=45° gives angular acceleration 2v²/L². Hence A.