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 as shown in figure. When string is cut, the initial angular acceleration of the rod is :
Answer & explanation
Correct answer: option 2
\(Torque : \tau = \vec{r} × \vec{F}\)
Also, \(\tau = I\alpha\)
For rod, I = \(\frac{ML^2}{3}\)
⇒Mg\(\frac{L}{2} = (\frac{ML^2}{3})\)
⇒\(\alpha = \frac{3g}{2l}\)