Question

A uniform rod PQ of length L is hinged at one end P. The rod is kept in the horizontal position by a massless string tied to point Q as shown in the figure. If the string is cut, the initial angular acceleration of the rod will be

• A. $\frac{g}{L}$
• B. $\frac{2g}{L}$
• C. $\frac{2g}{3L}$
• D. $\frac{3g}{2L}$

Answer 1

The correct option is D $\frac{3g}{2L}$


Once the string is cut,
${\tau }_0=I_0\alpha mg\frac{L}{2}=\frac{m{L}^2}{3}\alpha \Rightarrow \alpha =\frac{3g}{2L}$