Q. A rod PQ of mass M and length L is hinged at end P. The rod is kept horizontal by a massless string tied to point Q (the string is vertical). When the string is cut, the initial angular acceleration of the rod is
A) 3g/(2L)
B) g/L
C) 2g/L
D) 2g/(3L)
Explanation
[Solution from source] About the hinge P, the weight acts at L/2: torque = Mg(L/2). Moment of inertia of a rod about its end = ML²/3. α = Mg(L/2)/(ML²/3) = 3g/(2L). Using g/L treats the rod as a point mass at the end. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.